Patch merged into coreboot/master: chromeos: Allow for VB_SOURCE override

the following patch was just integrated into master:
commit c7ae731430ce9ffa78bb6752f70a4c5706560408
Author: Paul Kocialkowski 
Date:   Mon Aug 3 14:11:54 2015 +0200

chromeos: Allow for VB_SOURCE override

One may prefer to include vboot from another directory than 3rdparty for
    convenience. This is especially the case in Libreboot, where 3rdparty is not
    checked out at all.

Change-Id: I13167eb604a777a2ba87c3567f134ef3ff9610e4
    Signed-off-by: Paul Kocialkowski 
    Reviewed-on: http://review.coreboot.org/11116
    Tested-by: build bot (Jenkins)
    Reviewed-by: Patrick Georgi

See http://review.coreboot.org/11116 for details.

-gerrit