Ensure that no changes with warnings are committed. Although using `-Werror` is debatable [1][2]. [1] http://blog.flameeyes.eu/2009/02/future-proof-your-code-dont-use-werror [2] http://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html Change-Id: I402f2d82dd4087d8a575b0a85305a02ef04bb537 Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-on: http://review.coreboot.org/2441 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>