futility: don't pass CFLAGS into futility's build

cros_sdk puts weird stuff into CFLAGS and we never cares because we
don't use CFLAGS. futility's Makefiles do.

BUG=chromium:595715
BRANCH=none
TEST=none

Change-Id: I66898c7e66d808047b0326c7471c64eaae950b15
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://chromium-review.googlesource.com/336436
Commit-Ready: Patrick Georgi <pgeorgi@chromium.org>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
1 file changed