Refactor generation of shared library flags

CMAKE_SHARED_LIBRARY_<lang>_FLAGS has flags on various platforms for a
variety of purposes that are correlated with shared libraries but not
exclusive to them.  Refactor generation of these flags to use new
purpose-specific platform variables

  CMAKE_<lang>_COMPILE_OPTIONS_DLL
  CMAKE_<lang>_COMPILE_OPTIONS_PIC
  CMAKE_<lang>_COMPILE_OPTIONS_PIE

Activate the DLL flags specifically for shared libraries.  Add a new
POSITION_INDEPENDENT_CODE target property to activate PIC/PIE flags, and
default to true for shared libraries to preserve default behavior.
Initialize the new property from CMAKE_POSITION_INDEPENDENT_CODE to
allow easy global configuration in projects.

Although the default behavior is unchanged by this refactoring, the new
approach ignores CMAKE_SHARED_LIBRARY_<lang>_FLAGS completely.  We must
leave it set in case projects reference the value.  Furthermore, if a
project modifies CMAKE_SHARED_LIBRARY_<lang>_FLAGS it expects the new
value to be used.  Add policy CMP0018 to handle compatibility with
projects that modify this platform variable.

Add a PositionIndependentCode test on platforms where we can get
meaningful results.

1 files changed, 2 insertions, 5 deletions

diff --git a/Source/cmNinjaTargetGenerator.cxx b/Source/cmNinjaTargetGenerator.cxx
index 80007f1..b3394bb 100644
--- a/Source/cmNinjaTargetGenerator.cxx
+++ b/Source/cmNinjaTargetGenerator.cxx
@@ -140,11 +140,8 @@ cmNinjaTargetGenerator::ComputeFlagsForObject(cmSourceFile *source,
   //   }
 
   // Add shared-library flags if needed.
-  {
-  bool shared = ((this->Target->GetType() == cmTarget::SHARED_LIBRARY) ||
-                 (this->Target->GetType() == cmTarget::MODULE_LIBRARY));
-  this->GetLocalGenerator()->AddSharedFlags(flags, language.c_str(), shared);
-  }
+  this->LocalGenerator->AddCMP0018Flags(flags, this->Target,
+                                        language.c_str());
 
   // TODO: Handle response file.
   // Add include directory flags.