util/abuild: Avoid another git submodule invocation

.xcompile is generated before the submodules handling, but there's no
need for the submodules to be around, so skip here, too.

Change-Id: I60205f65b124a09067de5ae50f066b5cf64733f2
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44550
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

util/abuild/abuild

@@ -769,7 +769,7 @@ if ! mkdir -p "$TARGET"; then
 	exit 1
 fi
 
-$MAKE -C"${ROOT}" .xcompile || exit 1
+$MAKE -C"${ROOT}" UPDATED_SUBMODULES=1 .xcompile || exit 1
 
 customizing=$(echo "$customizing" | cut -c3-)
 if [ "$customizing" = "" ]; then