Patch merged into coreboot/master: xcompile: document all the variables!

the following patch was just integrated into master:
commit 74c86456af23171457464766e3f1072bf5dca490
Author: Patrick Georgi 
Date:   Mon Jan 25 18:15:08 2016 +0100

xcompile: document all the variables!

What's the exact difference between TARCH, TSUPP and TBFDARCHS? Fear no
    more, it's documented.

Change-Id: I18717eb1e20b1c0a82a485d391de2794a77c59ae
    Signed-off-by: Patrick Georgi 
    Reviewed-on: https://review.coreboot.org/13419
    Reviewed-by: Ronald G. Minnich 
    Tested-by: build bot (Jenkins)

See https://review.coreboot.org/13419 for details.

-gerrit