[coreboot] Two issues in the build system

[Mats Erik Andersson]

I have made two observations concerning 'buildtargets':

1) Romcc is generated in duplicate in fallback/ as well as normal/.
   Is this necessary? Both executable have identical md5-hashes.
   I do at least modify by hand the target 'normal/clean' to leave
   romcc for the next round of compilations. I would have expected
   the python generator to produce such alternatives by itself.

2) The dependencies of most targets are so shallow, that it is almost
   inevitable to perform a full clean in order to assemble a new
   normal.rom or fallback.rom, even after the smallest of changes.
   Is this intentional?

Regards,

Mats Erik Andersson