CMake: Add -T option to choose a generator toolset

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_TOOLSET and associated variable documentation to
hold the value persistently.

Add a RunCMake.GeneratorToolset test to cover basic "-T" option cases.
Verify that CMAKE_GENERATOR_TOOLSET is empty without -T, that -T is
rejected when the generator doesn't support it, and that two -T options
are always rejected.

1 files changed, 13 insertions, 0 deletions

diff --git a/Source/cmake.h b/Source/cmake.h
index f6fe0d6..7253b39 100644
--- a/Source/cmake.h
+++ b/Source/cmake.h
@@ -187,6 +187,14 @@ 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 toolset.
+  void SetGeneratorToolset(std::string const& ts)
+    { this->GeneratorToolset = ts; }
+
+  ///! Get the name of the selected generator-specific toolset.
+  std::string const& GetGeneratorToolset() const
+    { return this->GeneratorToolset; }
+
   ///! get the cmCachemManager used by this invocation of cmake
   cmCacheManager *GetCacheManager() { return this->CacheManager; }
 
@@ -418,6 +426,7 @@ protected:
   std::string StartOutputDirectory;
   bool SuppressDevWarnings;
   bool DoSuppressDevWarnings;
+  std::string GeneratorToolset;
 
   ///! read in a cmake list file to initialize the cache
   void ReadListFile(const std::vector<std::string>& args, const char *path);
@@ -528,6 +537,10 @@ private:
    "A makefile generator is responsible for generating a particular build " \
    "system.  Possible generator names are specified in the Generators " \
    "section."},\
+  {"-T <toolset-name>", "Specify toolset name if supported by generator.", \
+   "Some CMake generators support a toolset name to be given to the " \
+   "native build system to choose a compiler.  " \
+   "See native build system documentation for allowed toolset names."}, \
   {"-Wno-dev", "Suppress developer warnings.",\
    "Suppress warnings that are meant for the author"\
    " of the CMakeLists.txt files."},\