darwin: Remove ccache-induced clang warnings.

Using ccache on Darwin generates many puzzling warnings about
unused include paths. This patch modifies android-configure.sh
to detect this and remove the warnings.

For more details, read:

  http://petereisentraut.blogspot.fr/2011/05/ccache-and-clang.html

+ Restore color warning/error messages with ccache + clang

Change-Id: I1350e5b1a99996856cc8b5a706163d67cd8fbec6
Merge "darwin: Remove ccache-induced clang warnings."