Properly handle multi-target builds going simultaneously. Buildbot features need testing.
Fix for infinite recursion error.
when cleaning the repo, keep incomplete builds that are not stale. They could be in-progress (currently building.)
Hitting an in-progress build will return zero. Not an error.
little digestgen improvement
Have digestgen clean up bad links that it encounters.
Have buildbot handle return code 1 from buildrepo gracefully.
Don't use mtime stage3 date for buildbot. Use the timestamp.