title: How to execute shell command before compile task?
body: <p>I'd like to execute a shell command - <code>rm -r</code> a directory - whenever my sbt project builds. This would be before <code>compile</code>.</p>
  
  <p>Reasoning: There's a cache file that never gets updated. If I delete it before each compile, it forces the update.</p>
  
  <p>Please advise.</p>