SVN seems to die randomly *a lot* during
large updates for some users, and I'm no
closer to finding out why that keeps happening.
"The internet" seems to imply some AV vendors
may be at fault here but nothing conclusive.
The solution however is repeatedly running
`svn cleanup`and `svn update` in the library
folder to repair the corruption and finish the
update.
This change adds a small convenience helper
to automate the repair.
This is done inside the make.bat code rather
than the shared python based update code, since
python lives in the library folder and may
or may not exist when this corruption occurs.
