This also relates to an issue that I wanted to raise earlier: when doing a
search for files at <http://cygwin.com/packages/>, those files that are
created by postinstall scripts (e.g., symlinks) will not show up in the
listing.
So, it might be a good idea to keep a manifest of files that would be
potentially created by postinstall scripts, and to remove those files when
the package is removed. It's possible that setup will have a separate
mechanism for tracking this. Frankly, I don't have a concrete suggestion
on how to implement this, but thought I'd at least get this into the
archives and make people aware of the issues.