In order to migrate from symlinks to directories and try changes on trybots, we need to make sure all previously created symlinks are gone when bot_update is syncing the checkout. Otherwise we'll run into errors when symlinks exists in the locations where a directory is about to be created.
This can be solved by invoking setup_links.py --clean-only as a build step.
Comment 1 by kjellander@chromium.org
, Nov 8 2016