CMAKE_CXX_COMPILER_VERSION is not documented
The following variables are not documented in 3.8.1 (including the current git master/stage docs)
CMAKE_CXX_COMPILER_VERSION
CMAKE_C_COMPILER_VERSION
The following variables are not documented in 3.8.1 (including the current git master/stage docs)
CMAKE_CXX_COMPILER_VERSION
CMAKE_C_COMPILER_VERSION