Ceph

Although the following rule has been defined in the CMakeLists.txt, the 'diagnostics-color' option is added during source compiling while the gcc version is not actually support the option, typically, the gcc version lower than 4.9.

1. Handle diagnostics color if compiler supports them.
   CHECK_C_COMPILER_FLAG("-fdiagnostics-color=always"
   COMPILER_SUPPORTS_DIAGNOSTICS_COLOR)

The message from the CMakeError.log

/usr/bin/cc -Wall -Wtype-limits -Wignored-qualifiers -Winit-self -Wpointer-arith -Werror=format-security -fno-strict-aliasing -fsigned-char -rdynamic -Wno-unknown-pragmas -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=2 -std=gnu99 -DCOMPILER_SUPPORTS_DIAGNOSTICS_COLOR -fPIE -fdiagnostics-color=always -o CMakeFiles/cmTryCompileExec2260236235.dir/src.c.o -c /home/dave/gerrit/ceph/build/CMakeFiles/CMakeTmp/src.c
cc: error: unrecognized command line option '-fdiagnostics-color=always'
make¹: Leaving directory `/home/dave/gerrit/ceph/build/CMakeFiles/CMakeTmp'
make¹: * [CMakeFiles/cmTryCompileExec2260236235.dir/src.c.o] Error 1make: * [cmTryCompileExec2260236235/fast] Error 2