jenkins: fix: recent change broke jenkins build

Recent commit 851802b927ccfcb061a2774fdc5de12141426b5c introduces a build
branch, which works fine, but only on the first run. A second run in the same
repos can't delete the branch git is currently on.

I've had enough of git being impossibly difficult in UI to simply checkout a
hash or a branch now. Completely wipe out the git repository and clone a fresh
one every time.

Unfortunately, 'git clone -b' doesn't allow passing a commit hash, so we still
need to do a clone-then-checkout dance. At least now we know it will work the
same on every run.

Change-Id: I6aca4c53a796312248a189b815dfc1198a173ed9
1 file changed