dependency tracking for coreboot

dependency tracking for coreboot

Obviously compile time increases slightly because more work has to be done, but
I'm sure the benefit of having to rm -rf build less often is worth it :-)

Other small changes:
* be a bit more verbose on some of the created files
* move -O2 from compiler rule into bootblock_romccflags
* drop rule needed for util/*.c -> build/*.o as x86emu no longer lives in util.

Signed-off-by: Stefan Reinauer <stepan@coresystems.de>
Acked-by: Myles Watson <mylesgw@gmail.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5280 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1