cbuildbot: add Gnawty board builder configs

BUG=chromium:355137
TEST=buildbot/cbuildbot_config_unittest.py

Change-Id: I5a7284c900c2f302468ff076a058f17025021048
Reviewed-on: https://chromium-review.googlesource.com/191352
Reviewed-by: Peter Mayo <petermayo@chromium.org>
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
(cherry picked from commit d0884fab7980e96ade7f2a64e4c6fe0590e97a69)
Reviewed-on: https://chromium-review.googlesource.com/192452
1 file changed