romcc: Remove old test infrastructure, rework Makefile

Changes in visible behaviour:
 - The default make target doesn't run the tests anymore
 - All generated files are stored under util/romcc/build/
   (or $BUILD_DIR)

Change-Id: If003240742eb1902a6e9b337cdee299d7d66ee06
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/14341
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

util/romcc/test.sh

@@ -79,9 +79,9 @@ init_stats() {
 }
 
 get_romcc() {
-	ROMCC="$BASEDIR/romcc"
+	ROMCC="$BUILDDIR/romcc"
 	if [ ! -f "$ROMCC" ]; then
-		echo "romcc not found! Please run \"make romcc\"."
+		echo "romcc not found! Please run \"make\"."
 		exit 1
 	fi
 }