Build: GNUARM: add color diagnostics while using ninja generator

Add compile option '-fdiagnostics-color=always' as a workaround to a
bug in GCC for ninja build where the compiler output doesn't add color.
For reference: https://github.com/ninja-build/ninja/issues/174

Signed-off-by: Arnold Gabriel Benedict <arnoldgabriel.benedict@arm.com>
Change-Id: I36da3d659216e92c6e40ff4923f4548306fe712d
1 file changed