Allow creating firmware images without GBB

Do not fail creating an image in case '/config/nogbb' object is
present in the device tree, just do not build the GBB section in that
case.

BUG=chrome-os-partner:18329
TEST=manual
  . with the upcoming chromeos-bootimage and peach-u-boot modifications

   $ emerge-peach_pit chromeos-bootimage

   succeeds for both peach_pit and smdk5420 device trees.

Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>

Change-Id: I482a1e2686437cd06a25385f564b349bd91fe10b
Reviewed-on: https://gerrit.chromium.org/gerrit/47165
Tested-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
1 file changed