util: Update makefiles for junit testing

- Have clean remove junit.xml files.
- Remove junit.xml target from cbmem makefile - this is in the top
level Makefile.inc now.
- add distclean targets to makefiles.
- Make sure all makefiles have .PHONY set up.
- rm commands need -f or they will fail if the file they're trying
to remove doesn't exist, causing the build to fail.

Change-Id: I2f0635f2c0a9417e3377a90c8d67103323c4a72f
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: http://review.coreboot.org/12120
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
6 files changed