title: Heroku time out on deploy because of asset precompilation
body: <p>Problem: my Rails app won't deploy on Heroku (<code>Timed out compiling Ruby app (15 minutes)</code>)  because of assets precompilation.</p>
  
  <p>I use gems (asset_sync, sprockets-image_compressor, image_optim) that cause slow asset precompilation. I also sync my assets to store them on S3. I had not have this issue before adding sprockets-image_compressor and image_optim gems</p>
  
  <p>I could precompile assets locally but I would have to deal with my multiple environments (I have a staging app and a production app and I store my assets on different bucket on S3 regarding the environment) and I don't want to do that. And anyway that should be handled on deployment on Heroku.</p>
  
  <p>I've also opened a ticket on Heroku asking them to increase the time out but I doubt they'll do that.</p>
  
  <p>Any idea, suggestions?</p>