Patch merged into coreboot/master: build system: tighten down .xcompile handling some more

the following patch was just integrated into master:
commit 6dda31d287c3460398c90193419b72d75abc2d51
Author: Patrick Georgi 
Date:   Thu Nov 19 15:15:33 2015 +0100

build system: tighten down .xcompile handling some more

Bail out if .xcompile is incomplete or can't be regenerated.

Change-Id: I74adeded7a3e849b25bf65c5b02f67820f29c7e2
    Signed-off-by: Patrick Georgi 
    Reviewed-on: http://review.coreboot.org/12477
    Tested-by: build bot (Jenkins)
    Reviewed-by: Martin Roth

See http://review.coreboot.org/12477 for details.

-gerrit