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>
5 files changed