[CMake] Colored diagnostic output for GCC 4.9 through Ninja

[Robert Dailey]

On Wed, Oct 28, 2015 at 9:03 AM, Miller Henry <MillerHenry at johndeere.com> wrote:
>
> I do something like this, which works for clang and should work for gcc 4.9 though I haven't tested it.   I haven't wrote the right way to do this which is to check if the terminal supports color before passing the flag in. I don't know what will happen on our e.g. CI system which doesn't support color.
>
> macro(AddCXXFlagIfSupported flag test)
>    CHECK_CXX_COMPILER_FLAG(${flag} ${test})
>    if( ${${test}} )
>       message("adding ${flag}")
>       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}")
>    endif()
> endmacro()
>
> if("Ninja" STREQUAL ${CMAKE_GENERATOR})
>    AddCXXFlagIfSupported(-fcolor-diagnostics COMPILER_SUPPORTS_fcolor-diagnostics)
> endif()
>
> P.s. AddCXXFlagIfSupported ought to be in the default cmake distribution along with a lot or similar things

Unfortunately your solution doesn't seem to work. I get the following output:

[1/1] Re-running CMake...
-- Performing Test COMPILER_SUPPORTS_fcolor-diagnostics
-- Performing Test COMPILER_SUPPORTS_fcolor-diagnostics - Failed

GCC 4.9 supports this I thought?