Change formatting of ROM_NAME for the output zip for Windows file names (h/t viulian)

I didn't think about what would happen if the rom was being stored outside
the cygwin environment. Probably pretty common. The zips were
apparently coming out as, e.g. update-openpdroid-C:\OPENPD~1\CM-101~1.ZIP.

This should escape any Windows file names, if we find them. And since it has
barely been tested, maybe some unintended consequences as well! Supporting
Windows w/o a tester has been a real hassle since Kobik moved on.