futility: don't pass toolchain flags into futility's build

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

BUG=chromium:595715
BRANCH=none
TEST=none

Change-Id: I512d5adb55cad8b31dc29d9c076ecd5d9c701cf6
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 58739332ddba7ef759aac37f3a4410dd487f210f
Original-Change-Id: I66898c7e66d808047b0326c7471c64eaae950b15
Original-Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/336436
Original-Commit-Ready: Patrick Georgi <pgeorgi@chromium.org>
Original-Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/14237
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/util/futility/Makefile.inc b/util/futility/Makefile.inc
index 26b218d..d37be4b 100644
--- a/util/futility/Makefile.inc
+++ b/util/futility/Makefile.inc
@@ -2,7 +2,7 @@
 
 $(objutil)/futility/build/futility/futility:
 	@printf "    MAKE       $(subst $(objutil)/,,$(@))\n"
-	$(MAKE) -C $(VB_SOURCE) \
+	unset CFLAGS LDFLAGS; $(MAKE) -C $(VB_SOURCE) \
 		BUILD=$(abspath $@/../..) \
 		CC="$(HOSTCC)" \
 		V=$(V) \