Colour output from Ninja generator in CMake

Found in the BloatyMcBloatFace repository is this snippet to get coloured compiler output when using the Ninja generator from CMake.

# When using Ninja, compiler output won't be colorized without this.
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG(-fdiagnostics-color=always SUPPORTS_COLOR_ALWAYS)
if(SUPPORTS_COLOR_ALWAYS)
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fdiagnostics-color=always")
endif()