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, 8 insertions, 0 deletions

diff --git a/Source/cmDocumentVariables.cxx b/Source/cmDocumentVariables.cxx
index 08b3ef1..2b9104c 100644
--- a/Source/cmDocumentVariables.cxx
+++ b/Source/cmDocumentVariables.cxx
@@ -255,6 +255,14 @@ void cmDocumentVariables::DefineVariables(cmake* cm)
      "CMAKE_EXTRA_GENERATOR (e.g. \"Eclipse CDT4\").",false,
      "Variables that Provide Information");
   cm->DefineProperty
+    ("CMAKE_GENERATOR_TOOLSET", cmProperty::VARIABLE,
+     "Native build system toolset name specified by user.",
+     "Some CMake generators support a toolset name to be given to the "
+     "native build system to choose a compiler.  "
+     "If the user specifies a toolset name (e.g. via the cmake -T option) "
+     "the value will be available in this variable.",false,
+     "Variables that Provide Information");
+  cm->DefineProperty
     ("CMAKE_HOME_DIRECTORY", cmProperty::VARIABLE,
      "Path to top of source tree.",
      "This is the path to the top level of the source tree.",false,