Make the build tolerate re-definitions. Change-Id: Ia7505837c70b1f749262508b26576e95c7865576 Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com> Reviewed-on: http://review.coreboot.org/8609 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Georgi <pgeorgi@google.com>