Check*: Tolerate variables set with names of languages

Fix the language checks added by commit 90dead024c (CheckCompilerFlag:
unified way to check compiler flags per language, 2020-09-25,
v3.19.0-rc1~88^2), commit 10ae907de0 (CheckSoureCompiles: Add a unified
way to check if a source compiles, 2020-09-14, v3.19.0-rc1~118^2~1), and
commit 357e2ef429 (CheckSoureRuns: Add a unified way to check if a
source runs, 2020-09-14, v3.19.0-rc1~118^2) to work when variables of
the language names are set.

Fixes: #21500

3 files changed, 20 insertions, 20 deletions

diff --git a/Modules/Internal/CheckCompilerFlag.cmake b/Modules/Internal/CheckCompilerFlag.cmake
index f790d87..6b2a11e 100644
--- a/Modules/Internal/CheckCompilerFlag.cmake
+++ b/Modules/Internal/CheckCompilerFlag.cmake
@@ -11,20 +11,20 @@ cmake_policy(SET CMP0057 NEW) # if() supports IN_LIST
 
 function(CMAKE_CHECK_COMPILER_FLAG _lang _flag _var)
 
-  if(_lang STREQUAL C)
+  if(_lang STREQUAL "C")
     set(_lang_src "int main(void) { return 0; }")
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C")
-  elseif(_lang STREQUAL CXX)
+  elseif(_lang STREQUAL "CXX")
     set(_lang_src "int main() { return 0; }")
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+")
-    elseif(_lang STREQUAL CUDA)
+  elseif(_lang STREQUAL "CUDA")
     set(_lang_src "__host__ int main() { return 0; }")
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+" # Host GNU
                          FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL Fortran)
+  elseif(_lang STREQUAL "Fortran")
     set(_lang_src "       program test\n       stop\n       end program")
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Fortran")
-  elseif(_lang STREQUAL OBJC)
+  elseif(_lang STREQUAL "OBJC")
     set(_lang_src [=[
 #ifndef __OBJC__
 #  error "Not an Objective-C compiler"
@@ -32,7 +32,7 @@ function(CMAKE_CHECK_COMPILER_FLAG _lang _flag _var)
 int main(void) { return 0; }]=])
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C" # GNU
                          FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL OBJCXX)
+  elseif(_lang STREQUAL "OBJCXX")
     set(_lang_src [=[
 #ifndef __OBJC__
 #  error "Not an Objective-C++ compiler"
@@ -40,7 +40,7 @@ int main(void) { return 0; }]=])
 int main(void) { return 0; }]=])
     set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C\\+\\+" # GNU
                          FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL ISPC)
+  elseif(_lang STREQUAL "ISPC")
     set(_lang_src "float func(uniform int32, float a) { return a / 2.25; }")
   else()
     message (SEND_ERROR "check_compiler_flag: ${_lang}: unknown language.")
diff --git a/Modules/Internal/CheckSourceCompiles.cmake b/Modules/Internal/CheckSourceCompiles.cmake
index 91c8964..3b2152a 100644
--- a/Modules/Internal/CheckSourceCompiles.cmake
+++ b/Modules/Internal/CheckSourceCompiles.cmake
@@ -10,25 +10,25 @@ cmake_policy(SET CMP0057 NEW) # if() supports IN_LIST
 function(CMAKE_CHECK_SOURCE_COMPILES _lang _source _var)
   if(NOT DEFINED "${_var}")
 
-    if(_lang STREQUAL C)
+    if(_lang STREQUAL "C")
       set(_lang_textual "C")
       set(_lang_ext "c")
-    elseif(_lang STREQUAL CXX)
+    elseif(_lang STREQUAL "CXX")
       set(_lang_textual "C++")
       set(_lang_ext "cxx")
-    elseif(_lang STREQUAL CUDA)
+    elseif(_lang STREQUAL "CUDA")
       set(_lang_textual "CUDA")
       set(_lang_ext "cu")
-    elseif(_lang STREQUAL Fortran)
+    elseif(_lang STREQUAL "Fortran")
       set(_lang_textual "Fortran")
       set(_lang_ext "F90")
-    elseif(_lang STREQUAL ISPC)
+    elseif(_lang STREQUAL "ISPC")
       set(_lang_textual "ISPC")
       set(_lang_ext "ispc")
-    elseif(_lang STREQUAL OBJC)
+    elseif(_lang STREQUAL "OBJC")
       set(_lang_textual "Objective-C")
       set(_lang_ext "m")
-    elseif(_lang STREQUAL OBJCXX)
+    elseif(_lang STREQUAL "OBJCXX")
       set(_lang_textual "Objective-C++")
       set(_lang_ext "mm")
     else()
diff --git a/Modules/Internal/CheckSourceRuns.cmake b/Modules/Internal/CheckSourceRuns.cmake
index 3a4b758..676f3d0 100644
--- a/Modules/Internal/CheckSourceRuns.cmake
+++ b/Modules/Internal/CheckSourceRuns.cmake
@@ -10,22 +10,22 @@ cmake_policy(SET CMP0057 NEW) # if() supports IN_LIST
 function(CMAKE_CHECK_SOURCE_RUNS _lang _source _var)
   if(NOT DEFINED "${_var}")
 
-    if(_lang STREQUAL C)
+    if(_lang STREQUAL "C")
       set(_lang_textual "C")
       set(_lang_ext "c")
-    elseif(_lang STREQUAL CXX)
+    elseif(_lang STREQUAL "CXX")
       set(_lang_textual "C++")
       set(_lang_ext "cxx")
-    elseif(_lang STREQUAL CUDA)
+    elseif(_lang STREQUAL "CUDA")
       set(_lang_textual "CUDA")
       set(_lang_ext "cu")
-    elseif(_lang STREQUAL Fortran)
+    elseif(_lang STREQUAL "Fortran")
       set(_lang_textual "Fortran")
       set(_lang_ext "F90")
-    elseif(_lang STREQUAL OBJC)
+    elseif(_lang STREQUAL "OBJC")
       set(_lang_textual "Objective-C")
       set(_lang_ext "m")
-    elseif(_lang STREQUAL OBJCXX)
+    elseif(_lang STREQUAL "OBJCXX")
       set(_lang_textual "Objective-C++")
       set(_lang_ext "mm")
     else()