Remove .git/config.lock in build directory
git fetch mode, a build might get fail before the
git init step
fails if the
.git/config.lock file happens to exist for some reason.
We now prune this file just in case.
writeGitCleanup() to run before git init. We should be able to remove the lock files before the
git init runs, since
git init should not affect them. However,
.git/config.lock needs to be removed for
git init to succeed.
Encountered in #26618 (comment 452182599)