title: My cabal packages are FUBAR; how can I purge them and start over?
body: <p>I forgot to enable building libs for profiling in my <code>~/.cabal/config</code> before installing a bunch of packages on a new machine and now a <code>--reinstall world</code> to try to fix the situation has left everything broken (naturally). </p>
  
  <p>I think it's a better use of my time to just purge everything. How do I do that correctly?</p>