Tweak makefile to get GERRIT_BRANCH if defined

The way Jenkins jobs are checked out, the branch is not active, but
it is defined in the GERRIT_BRANCH env var. So if we can find that
defined, then that's the branch that should be built. If not, we can
just build the current branch.

Signed-off-by: Eric Ball <eball@linuxfoundation.org>
Change-Id: I2e149661f7a7f07ba3674cc60be4daaf396b08fe
2 files changed