If a baseboard exists in the build.mk for a board, use that
as the unibuild path.
BRANCH=none
BUG=b:77128456
TEST=tested the following command with correct results:
flash_ec --board=yorp (baseboard)
flash_ec --board=bip (baseboard)
flash_ec --board=grunt (non-baseboard)
Change-Id: Ic4573cb01849275d1333ff9e715f69a4c95444b0
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/986753
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>