message: Don't spawn threads for fresh work
  On "fresh" builds this ends up just wasting a lot of time!
diff: @@ -294,12 +294,16 @@ impl<'a> JobQueue<'a> {
  *self.counts.get_mut(key.pkg).unwrap() -= 1;
  let my_tx = self.tx.clone();
  - scope.spawn(move || {
  + let doit = move || {
  let res = job.run(fresh, &JobState {
  tx: my_tx.clone(),
  });
  my_tx.send(Message::Finish(key, res)).unwrap();
  - });
  + };
  + match fresh {
  + Freshness::Fresh => doit(),
  + Freshness::Dirty => { scope.spawn(doit); }
  + }
  // Print out some nice progress information
  self.note_working_on(config, &key, fresh)?;
  