CMake: Add CMAKE_GENERATOR_PLATFORM option

Reject the option by default.  It will be implemented on a per-generator
basis.  Pass the setting into try_compile project generation.  Add cache
entry CMAKE_GENERATOR_PLATFORM and associated variable documentation to
hold the value persistently.

Add a RunCMake.GeneratorPlatform test to cover basic use cases for the
option.  Verify that CMAKE_GENERATOR_PLATFORM is empty by default, and
that it is rejected when the generator does not support a user setting.

1 files changed, 4 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index f80c3c7..f166789 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -65,6 +65,10 @@ public:
   virtual bool SetSystemName(std::string const&, cmMakefile*)
     { return true; }
 
+  /** Set the generator-specific platform name.  Returns true if platform
+      is supported and false otherwise.  */
+  virtual bool SetGeneratorPlatform(std::string const& p, cmMakefile* mf);
+
   /** Set the generator-specific toolset name.  Returns true if toolset
       is supported and false otherwise.  */
   virtual bool SetGeneratorToolset(std::string const& ts, cmMakefile* mf);