-W is the old name for -Wextra, so let's rename it to be consistent with
the rest of the utility Makefiles.
Change-Id: I0e50f13d2617b785d343707fc895516574164562
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34455
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>