VS: Implement generator toolset selection (#10722, #13774)

Implement generator toolset selection (cmake -T) for VS >= 10 by setting
the PlatformToolset.  Extend the RunCMake.GeneratorToolset test case to
verify CMAKE_GENERATOR_TOOLSET when the generator supports -T.

Since commit 485a940e (VS: Simplify MSVC version reporting, 2012-08-23)
all MSVC version information is detected during the compiler id step
from the actual compiler invoked by generated build systems rather than
hard-coded in VS generators.  Therefore we can set the PlatformToolset
in VS >= 10 project files and support toolsets from other VS versions.

Source/cmGlobalVisualStudio10Generator.cxx

@@ -79,6 +79,14 @@ cmGlobalVisualStudio10Generator::cmGlobalVisualStudio10Generator(
     "ProductDir", vc10Express, cmSystemTools::KeyWOW64_32);
 }
 
+//----------------------------------------------------------------------------
+bool
+cmGlobalVisualStudio10Generator::SetGeneratorToolset(std::string const& ts)
+{
+  this->PlatformToolset = ts;
+  return true;
+}
+
 //----------------------------------------------------------------------------
 void cmGlobalVisualStudio10Generator::AddPlatformDefinitions(cmMakefile* mf)
 {

Source/cmGlobalVisualStudio10Generator.h

@@ -28,6 +28,8 @@ public:
     const char* architectureId, const char* additionalPlatformDefinition);
   static cmGlobalGeneratorFactory* NewFactory();
 
+  virtual bool SetGeneratorToolset(std::string const& ts);
+
   virtual std::string
   GenerateBuildCommand(const char* makeProgram,
                        const char *projectName,

Source/cmake.h

@@ -540,6 +540,8 @@ private:
   {"-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.  " \
+   "This is supported only on specific generators:\n" \
+   "  Visual Studio >= 10\n" \
    "See native build system documentation for allowed toolset names."}, \
   {"-Wno-dev", "Suppress developer warnings.",\
    "Suppress warnings that are meant for the author"\

Tests/RunCMake/GeneratorToolset/RunCMakeTest.cmake

@@ -2,9 +2,15 @@ include(RunCMake)
 
 run_cmake(NoToolset)
 
+if("${RunCMake_GENERATOR}" MATCHES "Visual Studio 1[01]")
+  set(RunCMake_TEST_OPTIONS -T "Test Toolset")
+  run_cmake(TestToolset)
+  unset(RunCMake_TEST_OPTIONS)
+else()
   set(RunCMake_TEST_OPTIONS -T "Bad Toolset")
   run_cmake(BadToolset)
   unset(RunCMake_TEST_OPTIONS)
+endif()
 
 set(RunCMake_TEST_OPTIONS -T "Toolset 1" "-TToolset 2")
 run_cmake(TwoToolsets)

Tests/RunCMake/GeneratorToolset/TestToolset-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/GeneratorToolset/TestToolset-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at TestToolset.cmake:2 \(message\):
+  CMAKE_GENERATOR_TOOLSET is "Test Toolset" as expected.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/GeneratorToolset/TestToolset.cmake

@@ -0,0 +1,7 @@
+if("x${CMAKE_GENERATOR_TOOLSET}" STREQUAL "xTest Toolset")
+  message(FATAL_ERROR "CMAKE_GENERATOR_TOOLSET is \"Test Toolset\" as expected.")
+else()
+  message(FATAL_ERROR
+    "CMAKE_GENERATOR_TOOLSET is \"${CMAKE_GENERATOR_TOOLSET}\" "
+    "but should be \"Test Toolset\"!")
+endif()