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, 9 insertions, 0 deletions

diff --git a/Source/cmake.h b/Source/cmake.h
index 2d04902..919fc24 100644
--- a/Source/cmake.h
+++ b/Source/cmake.h
@@ -191,6 +191,14 @@ class cmake
   ///! Get the names of the current registered generators
   void GetRegisteredGenerators(std::vector<std::string>& names);
 
+  ///! Set the name of the selected generator-specific platform.
+  void SetGeneratorPlatform(std::string const& ts)
+    { this->GeneratorPlatform = ts; }
+
+  ///! Get the name of the selected generator-specific platform.
+  std::string const& GetGeneratorPlatform() const
+    { return this->GeneratorPlatform; }
+
   ///! Set the name of the selected generator-specific toolset.
   void SetGeneratorToolset(std::string const& ts)
     { this->GeneratorToolset = ts; }
@@ -403,6 +411,7 @@ protected:
   std::string StartOutputDirectory;
   bool SuppressDevWarnings;
   bool DoSuppressDevWarnings;
+  std::string GeneratorPlatform;
   std::string GeneratorToolset;
 
   ///! read in a cmake list file to initialize the cache