This should reduce/eliminate the amount of manual cleanup users
have to do to sync past 177567c518b121731e507e9b9c4049c4dc96e4c8 (#15754).
This is essentially a stripped down version of
526248779a/setup_links.py
which only does the link cleaning + adds removal of the links db.
BUG=webrtc:5006
NOTRY=True
Review-Url: https://codereview.webrtc.org/2603203002
Cr-Commit-Position: refs/heads/master@{#15897}
