Change in coreboot[master]: Makefile.inc: Fix dependency tracking of fmap{_config.h, .desc}

[Alex Thiessen (Code Review)]

Alex Thiessen has posted comments on this change. ( https://review.coreboot.org/28198 )

Change subject: Makefile.inc: Fix dependency tracking of fmap{_config.h,.desc}
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Patch Set 2:

The code looks quite strange and in fact, these are false dependencies. If you e.g. `touch fmap.fmap`, `make` will call `true` in an attempt to update `fmap_config.h`, every time without real success.

If you have a recipe like the one for `fmap.fmap` that builds a number of targets, then the right thing to do is to define multiple targets in the rule: https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html

Feel free to update the fix :)