Honor CMAKE_<LANG>_FLAGS[_<CONFIG>]_INIT set in toolchain files

Document these variables.

Change our convention for setting these variables from:

    set(CMAKE_C_FLAGS_INIT "...")

to

    string(APPEND CMAKE_C_FLAGS_INIT " ...")

so that any value previously set by a toolchain file will be used.

Automate the conversion with:

    sed -i 's/set *(\(CMAKE_\(C\|CXX\|Fortran\|RC\|ASM\|${[^}]\+}\)_FLAGS\(_[^_]\+\)\?_INIT \+"\)/string(APPEND \1 /' \
      Modules/Compiler/*.cmake Modules/Platform/*.cmake

and follow up with some manual fixes (e.g. to cases that already
meant to append).  Also revert the automated changes to contexts
that are not protected from running multiple times.

36 files changed, 149 insertions, 149 deletions

diff --git a/Modules/Compiler/ARMCC.cmake b/Modules/Compiler/ARMCC.cmake
index 3cf628c..2ec75c3 100644
--- a/Modules/Compiler/ARMCC.cmake
+++ b/Modules/Compiler/ARMCC.cmake
@@ -20,11 +20,11 @@ set(CMAKE_AR "${CMAKE_ARMCC_AR}" CACHE FILEPATH "The ARMCC archiver" FORCE)
 mark_as_advanced(CMAKE_ARMCC_AR)
 
 macro(__compiler_armcc lang)
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Ospace -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-Otime -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Ospace -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -Otime -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 
   set(CMAKE_${lang}_OUTPUT_EXTENSION ".o")
   set(CMAKE_${lang}_OUTPUT_EXTENSION_REPLACE 1)
diff --git a/Modules/Compiler/Absoft-Fortran.cmake b/Modules/Compiler/Absoft-Fortran.cmake
index 2e1666f..da1fc80 100644
--- a/Modules/Compiler/Absoft-Fortran.cmake
+++ b/Modules/Compiler/Absoft-Fortran.cmake
@@ -1,8 +1,8 @@
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 set(CMAKE_Fortran_MODDIR_FLAG "-YMOD_OUT_DIR=")
 set(CMAKE_Fortran_MODPATH_FLAG "-p")
 set(CMAKE_Fortran_VERBOSE_FLAG "-v")
diff --git a/Modules/Compiler/Bruce-C.cmake b/Modules/Compiler/Bruce-C.cmake
index 23676ec..cfabe65 100644
--- a/Modules/Compiler/Bruce-C.cmake
+++ b/Modules/Compiler/Bruce-C.cmake
@@ -1,7 +1,7 @@
 # Bruce C Compiler ignores "-g" flag and optimization cannot be
 # enabled here (it is implemented only for 8086 target).
-set (CMAKE_C_FLAGS_INIT "-D__CLASSIC_C__")
-set (CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set (CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " -D__CLASSIC_C__")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
diff --git a/Modules/Compiler/G95-Fortran.cmake b/Modules/Compiler/G95-Fortran.cmake
index fd84848..2c83fb8 100644
--- a/Modules/Compiler/G95-Fortran.cmake
+++ b/Modules/Compiler/G95-Fortran.cmake
@@ -1,8 +1,8 @@
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -Os")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 set(CMAKE_Fortran_MODDIR_FLAG "-fmod=")
 set(CMAKE_Fortran_VERBOSE_FLAG "-v")
 set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
diff --git a/Modules/Compiler/GHS-C.cmake b/Modules/Compiler/GHS-C.cmake
index 3072715..c30bdec 100644
--- a/Modules/Compiler/GHS-C.cmake
+++ b/Modules/Compiler/GHS-C.cmake
@@ -3,11 +3,11 @@ include(Compiler/GHS)
 set(CMAKE_C_VERBOSE_FLAG "-v")
 set(CMAKE_C_OUTPUT_EXTENSION ".o")
 
-set(CMAKE_C_FLAGS_INIT "")
-set(CMAKE_C_FLAGS_DEBUG_INIT "-Odebug -g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-Ospace")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-O")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O -g")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -Odebug -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -Ospace")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -O")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -O -g")
 
 set(CMAKE_C_GHS_KERNEL_FLAGS_DEBUG_INIT "-ldebug ${CMAKE_C_FLAGS_DEBUG_INIT}")
 set(CMAKE_C_GHS_KERNEL_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT}")
diff --git a/Modules/Compiler/GHS-CXX.cmake b/Modules/Compiler/GHS-CXX.cmake
index a51591b..b3018a7 100644
--- a/Modules/Compiler/GHS-CXX.cmake
+++ b/Modules/Compiler/GHS-CXX.cmake
@@ -3,11 +3,11 @@ include(Compiler/GHS)
 set(CMAKE_CXX_VERBOSE_FLAG "-v")
 set(CMAKE_CXX_OUTPUT_EXTENSION ".o")
 
-set(CMAKE_CXX_FLAGS_INIT "")
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-Odebug -g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-Ospace")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "-O")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O -g")
+string(APPEND CMAKE_CXX_FLAGS_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -Odebug -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -Ospace")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -O")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -O -g")
 
 set(CMAKE_CXX_GHS_KERNEL_FLAGS_DEBUG_INIT
   "-ldebug ${CMAKE_CXX_FLAGS_DEBUG_INIT}")
diff --git a/Modules/Compiler/GNU-Fortran.cmake b/Modules/Compiler/GNU-Fortran.cmake
index e9c8a59..fc848ac 100644
--- a/Modules/Compiler/GNU-Fortran.cmake
+++ b/Modules/Compiler/GNU-Fortran.cmake
@@ -5,8 +5,8 @@ set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
 set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
 
 # No -DNDEBUG for Fortran.
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -Os")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
 
 # No -isystem for Fortran because it will not find .mod files.
 unset(CMAKE_INCLUDE_SYSTEM_FLAG_Fortran)
diff --git a/Modules/Compiler/GNU.cmake b/Modules/Compiler/GNU.cmake
index c2d393d..34d4eaf 100644
--- a/Modules/Compiler/GNU.cmake
+++ b/Modules/Compiler/GNU.cmake
@@ -45,11 +45,11 @@ macro(__compiler_gnu lang)
   endif()
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g -DNDEBUG")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
   if(NOT APPLE OR NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4) # work around #4462
diff --git a/Modules/Compiler/Intel.cmake b/Modules/Compiler/Intel.cmake
index ff62804..8c3942c 100644
--- a/Modules/Compiler/Intel.cmake
+++ b/Modules/Compiler/Intel.cmake
@@ -27,10 +27,10 @@ else()
   macro(__compiler_intel lang)
     set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
-    set(CMAKE_${lang}_FLAGS_INIT "")
-    set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-    set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os")
-    set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3")
-    set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+    string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+    string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+    string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os")
+    string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3")
+    string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
   endmacro()
 endif()
diff --git a/Modules/Compiler/PGI-C.cmake b/Modules/Compiler/PGI-C.cmake
index da88c01..85d6e7e 100644
--- a/Modules/Compiler/PGI-C.cmake
+++ b/Modules/Compiler/PGI-C.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PGI)
 __compiler_pgi(C)
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PGI-CXX.cmake b/Modules/Compiler/PGI-CXX.cmake
index 97c9555..896e298 100644
--- a/Modules/Compiler/PGI-CXX.cmake
+++ b/Modules/Compiler/PGI-CXX.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PGI)
 __compiler_pgi(CXX)
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PGI-Fortran.cmake b/Modules/Compiler/PGI-Fortran.cmake
index 2866254..3765079 100644
--- a/Modules/Compiler/PGI-Fortran.cmake
+++ b/Modules/Compiler/PGI-Fortran.cmake
@@ -4,7 +4,7 @@ __compiler_pgi(Fortran)
 set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-Mnofreeform")
 set(CMAKE_Fortran_FORMAT_FREE_FLAG "-Mfreeform")
 
-set(CMAKE_Fortran_FLAGS_INIT "${CMAKE_Fortran_FLAGS_INIT} -Mpreprocess -Kieee")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "${CMAKE_Fortran_FLAGS_DEBUG_INIT} -Mbounds")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " -Mpreprocess -Kieee")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -Mbounds")
 
 set(CMAKE_Fortran_MODDIR_FLAG "-module ")
diff --git a/Modules/Compiler/PGI.cmake b/Modules/Compiler/PGI.cmake
index 797945f..51069c2 100644
--- a/Modules/Compiler/PGI.cmake
+++ b/Modules/Compiler/PGI.cmake
@@ -23,11 +23,11 @@ macro(__compiler_pgi lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g -O0")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O2 -s")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-fast -O3 -Mipa=fast")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -gopt")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g -O0")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O2 -s")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -fast -O3 -Mipa=fast")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -gopt")
 
   # Preprocessing and assembly rules.
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
diff --git a/Modules/Compiler/PathScale-C.cmake b/Modules/Compiler/PathScale-C.cmake
index 9db54af..94c7d08 100644
--- a/Modules/Compiler/PathScale-C.cmake
+++ b/Modules/Compiler/PathScale-C.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PathScale)
 __compiler_pathscale(C)
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PathScale-CXX.cmake b/Modules/Compiler/PathScale-CXX.cmake
index 4dd7660..276b81b 100644
--- a/Modules/Compiler/PathScale-CXX.cmake
+++ b/Modules/Compiler/PathScale-CXX.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PathScale)
 __compiler_pathscale(CXX)
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PathScale.cmake b/Modules/Compiler/PathScale.cmake
index 107f779..09ee2ba 100644
--- a/Modules/Compiler/PathScale.cmake
+++ b/Modules/Compiler/PathScale.cmake
@@ -23,9 +23,9 @@ macro(__compiler_pathscale lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g -O0")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-g -O2")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g -O0")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -g -O2")
 endmacro()
diff --git a/Modules/Compiler/SunPro-ASM.cmake b/Modules/Compiler/SunPro-ASM.cmake
index 2fa8b99..0d67400 100644
--- a/Modules/Compiler/SunPro-ASM.cmake
+++ b/Modules/Compiler/SunPro-ASM.cmake
@@ -8,11 +8,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_ASM_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_ASM_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_ASM_FLAG "-h")
 
-set(CMAKE_ASM_FLAGS_INIT "")
-set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_ASM_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_INIT " ")
+string(APPEND CMAKE_ASM_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_ASM_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize ASM link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-C.cmake b/Modules/Compiler/SunPro-C.cmake
index c452983..503684a 100644
--- a/Modules/Compiler/SunPro-C.cmake
+++ b/Modules/Compiler/SunPro-C.cmake
@@ -7,11 +7,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-h")
 
-set(CMAKE_C_FLAGS_INIT "")
-set(CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-CXX.cmake b/Modules/Compiler/SunPro-CXX.cmake
index b4a5591..ce01cdd 100644
--- a/Modules/Compiler/SunPro-CXX.cmake
+++ b/Modules/Compiler/SunPro-CXX.cmake
@@ -7,11 +7,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_CXX_FLAG "-h")
 
-set(CMAKE_CXX_FLAGS_INIT "")
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-Fortran.cmake b/Modules/Compiler/SunPro-Fortran.cmake
index 610e191..a0e07d4 100644
--- a/Modules/Compiler/SunPro-Fortran.cmake
+++ b/Modules/Compiler/SunPro-Fortran.cmake
@@ -10,11 +10,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_Fortran_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_Fortran_FLAG "-h")
 set(CMAKE_EXECUTABLE_RUNTIME_Fortran_FLAG "-R")
 
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 set(CMAKE_Fortran_MODDIR_FLAG "-moddir=")
 set(CMAKE_Fortran_MODPATH_FLAG "-M")
 
diff --git a/Modules/Compiler/TinyCC-C.cmake b/Modules/Compiler/TinyCC-C.cmake
index f7937ac..fbd2841 100644
--- a/Modules/Compiler/TinyCC-C.cmake
+++ b/Modules/Compiler/TinyCC-C.cmake
@@ -1,8 +1,8 @@
 set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-shared")
 
 # no optimization in tcc:
-set (CMAKE_C_FLAGS_INIT "")
-set (CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set (CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
diff --git a/Modules/Compiler/XL-ASM.cmake b/Modules/Compiler/XL-ASM.cmake
index 212179e..9177b39 100644
--- a/Modules/Compiler/XL-ASM.cmake
+++ b/Modules/Compiler/XL-ASM.cmake
@@ -2,11 +2,11 @@ set(CMAKE_ASM_VERBOSE_FLAG "-V")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_ASM_FLAGS_INIT "-qthreaded -qhalt=e -qsourcetype=assembler")
+string(APPEND CMAKE_ASM_FLAGS_INIT " -qthreaded -qhalt=e -qsourcetype=assembler")
 
-set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_ASM_FLAGS_RELEASE_INIT "-O -DNDEBUG")
-set(CMAKE_ASM_FLAGS_MINSIZEREL_INIT "-O -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_ASM_FLAGS_RELEASE_INIT " -O -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_MINSIZEREL_INIT " -O -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
 
 set(CMAKE_ASM_SOURCE_FILE_EXTENSIONS s )
diff --git a/Modules/Compiler/XL-C.cmake b/Modules/Compiler/XL-C.cmake
index 97dd017..f976c99 100644
--- a/Modules/Compiler/XL-C.cmake
+++ b/Modules/Compiler/XL-C.cmake
@@ -1,8 +1,8 @@
 include(Compiler/XL)
 __compiler_xl(C)
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_C_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_C_FLAGS_INIT " -qthreaded -qhalt=e")
diff --git a/Modules/Compiler/XL-CXX.cmake b/Modules/Compiler/XL-CXX.cmake
index 41372c1..545d657 100644
--- a/Modules/Compiler/XL-CXX.cmake
+++ b/Modules/Compiler/XL-CXX.cmake
@@ -1,11 +1,11 @@
 include(Compiler/XL)
 __compiler_xl(CXX)
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_CXX_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_CXX_FLAGS_INIT " -qthreaded -qhalt=e")
 
 set(CMAKE_CXX_COMPILE_OBJECT
   "<CMAKE_CXX_COMPILER> -+ <DEFINES> <INCLUDES> <FLAGS> -o <OBJECT> -c <SOURCE>")
diff --git a/Modules/Compiler/XL-Fortran.cmake b/Modules/Compiler/XL-Fortran.cmake
index ae9df4e..6bab6f6 100644
--- a/Modules/Compiler/XL-Fortran.cmake
+++ b/Modules/Compiler/XL-Fortran.cmake
@@ -10,7 +10,7 @@ set(CMAKE_Fortran_DEFINE_FLAG "-WF,-D")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_Fortran_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " -qthreaded -qhalt=e")
 
 # xlf: 1501-214 (W) command option E reserved for future use - ignored
 set(CMAKE_Fortran_CREATE_PREPROCESSED_SOURCE)
diff --git a/Modules/Compiler/XL.cmake b/Modules/Compiler/XL.cmake
index bf4f554..1f2b145 100644
--- a/Modules/Compiler/XL.cmake
+++ b/Modules/Compiler/XL.cmake
@@ -29,10 +29,10 @@ macro(__compiler_xl lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-V")
   set(CMAKE_${lang}_COMPILE_OPTIONS_PIC "-qpic")
 
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-g")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -g")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE     "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
 
diff --git a/Modules/Platform/ARTOS-GNU-C.cmake b/Modules/Platform/ARTOS-GNU-C.cmake
index 967d0e7..fe8d782 100644
--- a/Modules/Platform/ARTOS-GNU-C.cmake
+++ b/Modules/Platform/ARTOS-GNU-C.cmake
@@ -1,9 +1,9 @@
 # Define ARTOS to select proper behaviour and tell preprocessor to accept C++ style comments.
-set(CMAKE_C_FLAGS_INIT "-DARTOS -Xp -+")
+string(APPEND CMAKE_C_FLAGS_INIT " -DARTOS -Xp -+")
 # ac doesn't support -g properly and doesn't support the normal gcc optimization options. Just use the defaults set by ac.
-set(CMAKE_C_FLAGS_DEBUG_INIT "")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " ")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -DNDEBUG")
 # Most projects expect the stdio functions to be available.
 set(CMAKE_C_STANDARD_LIBRARIES_INIT "stdio.a")
diff --git a/Modules/Platform/Generic-ADSP-C.cmake b/Modules/Platform/Generic-ADSP-C.cmake
index 4b9ed9d..de1cee2 100644
--- a/Modules/Platform/Generic-ADSP-C.cmake
+++ b/Modules/Platform/Generic-ADSP-C.cmake
@@ -4,10 +4,10 @@ include(Platform/Generic-ADSP-Common)
 
 set(CMAKE_C_OUTPUT_EXTENSION ".doj")
 
-set(CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_C_FLAGS_RELEASE_INIT "")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " ")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " ")
 
 set(CMAKE_C_CREATE_STATIC_LIBRARY
     "<CMAKE_C_COMPILER> -build-lib -proc ${ADSP_PROCESSOR} -si-revision ${ADSP_PROCESSOR_SILICIUM_REVISION} -o <TARGET> <CMAKE_C_LINK_FLAGS> <OBJECTS>")
diff --git a/Modules/Platform/Generic-ADSP-CXX.cmake b/Modules/Platform/Generic-ADSP-CXX.cmake
index 9673aef..0cde8f2 100644
--- a/Modules/Platform/Generic-ADSP-CXX.cmake
+++ b/Modules/Platform/Generic-ADSP-CXX.cmake
@@ -2,10 +2,10 @@ include(Platform/Generic-ADSP-Common)
 
 set(CMAKE_CXX_OUTPUT_EXTENSION ".doj")
 
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " ")
 
 set(CMAKE_CXX_CREATE_STATIC_LIBRARY
      "<CMAKE_CXX_COMPILER> -build-lib -proc ${ADSP_PROCESSOR} -si-revision ${ADSP_PROCESSOR_SILICIUM_REVISION} -o <TARGET> <CMAKE_CXX_LINK_FLAGS> <OBJECTS>")
diff --git a/Modules/Platform/Generic-SDCC-C.cmake b/Modules/Platform/Generic-SDCC-C.cmake
index a1ca812..bbefe19 100644
--- a/Modules/Platform/Generic-SDCC-C.cmake
+++ b/Modules/Platform/Generic-SDCC-C.cmake
@@ -30,7 +30,7 @@ set(CMAKE_AR "${SDCCLIB_EXECUTABLE}" CACHE FILEPATH "The sdcc librarian" FORCE)
 
 # CMAKE_C_FLAGS_INIT and CMAKE_EXE_LINKER_FLAGS_INIT should be set in a CMAKE_SYSTEM_PROCESSOR file
 if(NOT DEFINED CMAKE_C_FLAGS_INIT)
-  set(CMAKE_C_FLAGS_INIT "-mmcs51 --model-small")
+  string(APPEND CMAKE_C_FLAGS_INIT " -mmcs51 --model-small")
 endif()
 
 if(NOT DEFINED CMAKE_EXE_LINKER_FLAGS_INIT)
diff --git a/Modules/Platform/HP-UX-HP-CXX.cmake b/Modules/Platform/HP-UX-HP-CXX.cmake
index 6d90191..d37d2b0 100644
--- a/Modules/Platform/HP-UX-HP-CXX.cmake
+++ b/Modules/Platform/HP-UX-HP-CXX.cmake
@@ -8,7 +8,7 @@ set(CMAKE_CXX_CREATE_ASSEMBLY_SOURCE
   "rm -f `basename \"<SOURCE>\" | sed 's/\\.[^./]*$$//'`.o"
   )
 
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "+O3 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "+O2 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " +O3 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " +O2 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -g")
diff --git a/Modules/Platform/HP-UX-HP.cmake b/Modules/Platform/HP-UX-HP.cmake
index 3935c31..398d6fb 100644
--- a/Modules/Platform/HP-UX-HP.cmake
+++ b/Modules/Platform/HP-UX-HP.cmake
@@ -27,7 +27,7 @@ macro(__hpux_compiler_hp lang)
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG_SEP ":")
   set(CMAKE_SHARED_LIBRARY_SONAME_${lang}_FLAG "-Wl,+h")
 
-  set(CMAKE_${lang}_FLAGS_INIT "")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
 
   set(CMAKE_${lang}_LINK_FLAGS "-Wl,+s,+nodefaultrpath")
 endmacro()
diff --git a/Modules/Platform/Windows-Embarcadero.cmake b/Modules/Platform/Windows-Embarcadero.cmake
index 102e3a6..8a87db3 100644
--- a/Modules/Platform/Windows-Embarcadero.cmake
+++ b/Modules/Platform/Windows-Embarcadero.cmake
@@ -132,10 +132,10 @@ macro(__embarcadero_language lang)
     )
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "${_tM}")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-Od -v")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O1 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O2 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-Od")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_tM}")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -Od -v")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O1 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O2 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -Od")
   set(CMAKE_${lang}_STANDARD_LIBRARIES_INIT "import32.lib")
 endmacro()
diff --git a/Modules/Platform/Windows-Intel-Fortran.cmake b/Modules/Platform/Windows-Intel-Fortran.cmake
index 1b93db8..3981a09 100644
--- a/Modules/Platform/Windows-Intel-Fortran.cmake
+++ b/Modules/Platform/Windows-Intel-Fortran.cmake
@@ -4,8 +4,8 @@ set(_COMPILE_Fortran " /fpp")
 set(CMAKE_Fortran_MODDIR_FLAG "-module:")
 set(CMAKE_Fortran_STANDARD_LIBRARIES_INIT "user32.lib")
 __windows_compiler_intel(Fortran)
-set (CMAKE_Fortran_FLAGS_INIT "/W1 /nologo /fpp /libs:dll /threads")
-set (CMAKE_Fortran_FLAGS_DEBUG_INIT "/Od /debug:full /dbglibs")
-set (CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "/O1 /DNDEBUG")
-set (CMAKE_Fortran_FLAGS_RELEASE_INIT "/O2 /DNDEBUG")
-set (CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "/O2 /debug:full /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " /W1 /nologo /fpp /libs:dll /threads")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " /Od /debug:full /dbglibs")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " /O1 /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " /O2 /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " /O2 /debug:full /DNDEBUG")
diff --git a/Modules/Platform/Windows-MSVC.cmake b/Modules/Platform/Windows-MSVC.cmake
index 3fd6802..b1969a2 100644
--- a/Modules/Platform/Windows-MSVC.cmake
+++ b/Modules/Platform/Windows-MSVC.cmake
@@ -303,17 +303,17 @@ macro(__windows_compiler_msvc lang)
     if(CMAKE_VS_PLATFORM_TOOLSET MATCHES "v[0-9]+_clang_.*")
       # note: MSVC 14 2015 Update 1 sets -fno-ms-compatibility by default, but this does not allow one to compile many projects
       # that include MS's own headers. CMake itself is affected project too.
-      set(CMAKE_${lang}_FLAGS_INIT "${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS -Wall${_FLAGS_${lang}}")
-      set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-D_DEBUG /MDd -gline-tables-only -fno-inline -O0 ${_RTC1}")
-      set(CMAKE_${lang}_FLAGS_RELEASE_INIT "/MD -O2 -DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "/MD -gline-tables-only -O2 -fno-inline -DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "/MD -DNDEBUG") # TODO: Add '-Os' once VS generator maps it properly for Clang
+      string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS -Wall${_FLAGS_${lang}}")
+      string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -D_DEBUG /MDd -gline-tables-only -fno-inline -O0 ${_RTC1}")
+      string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " /MD -O2 -DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " /MD -gline-tables-only -O2 -fno-inline -DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " /MD -DNDEBUG") # TODO: Add '-Os' once VS generator maps it properly for Clang
     else()
-      set(CMAKE_${lang}_FLAGS_INIT "${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS /W3${_FLAGS_${lang}}")
-      set(CMAKE_${lang}_FLAGS_DEBUG_INIT "/D_DEBUG /MDd /Zi /Ob0 /Od ${_RTC1}")
-      set(CMAKE_${lang}_FLAGS_RELEASE_INIT "/MD /O2 /Ob2 /DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "/MD /Zi /O2 /Ob1 /DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "/MD /O1 /Ob1 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS /W3${_FLAGS_${lang}}")
+      string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " /D_DEBUG /MDd /Zi /Ob0 /Od ${_RTC1}")
+      string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " /MD /O2 /Ob2 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " /MD /Zi /O2 /Ob1 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " /MD /O1 /Ob1 /DNDEBUG")
     endif()
   endif()
   set(CMAKE_${lang}_LINKER_SUPPORTS_PDB ON)
@@ -323,7 +323,7 @@ macro(__windows_compiler_msvc lang)
     set(CMAKE_RC_COMPILER_INIT rc)
   endif()
   if(NOT CMAKE_RC_FLAGS_INIT)
-    set(CMAKE_RC_FLAGS_INIT "${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
+    string(APPEND CMAKE_RC_FLAGS_INIT " ${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
   endif()
 
   enable_language(RC)
diff --git a/Modules/Platform/Windows-OpenWatcom.cmake b/Modules/Platform/Windows-OpenWatcom.cmake
index 7147600..269f923 100644
--- a/Modules/Platform/Windows-OpenWatcom.cmake
+++ b/Modules/Platform/Windows-OpenWatcom.cmake
@@ -52,13 +52,13 @@ set(CMAKE_BUILD_TYPE_INIT Debug)
 # single/multi-threaded                 /-bm
 # static/DLL run-time libraries         /-br
 # default is setup for multi-threaded + DLL run-time libraries
-set (CMAKE_C_FLAGS_INIT "-bt=nt -w3 -dWIN32 -br -bm")
-set (CMAKE_CXX_FLAGS_INIT "-bt=nt -xs -w3 -dWIN32 -br -bm")
+string(APPEND CMAKE_C_FLAGS_INIT " -bt=nt -w3 -dWIN32 -br -bm")
+string(APPEND CMAKE_CXX_FLAGS_INIT " -bt=nt -xs -w3 -dWIN32 -br -bm")
 foreach(lang C CXX)
-  set (CMAKE_${lang}_FLAGS_DEBUG_INIT "-d2")
-  set (CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-s -os -d0 -dNDEBUG")
-  set (CMAKE_${lang}_FLAGS_RELEASE_INIT "-s -ot -d0 -dNDEBUG")
-  set (CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-s -ot -d1 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -d2")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -s -os -d0 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -s -ot -d0 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -s -ot -d1 -dNDEBUG")
 endforeach()
 
 foreach(type CREATE_SHARED_LIBRARY CREATE_SHARED_MODULE LINK_EXECUTABLE)