title: Error: Multi dex requires Build Tools version
body: <p>I just updated my android studio and i'm getting this error:</p>
  
  <pre><code>Error:Execution failed for task
  ':app:transformClassesWithDexForDebug'.
  com.android.build.api.transform.TransformException:
  java.lang.RuntimeException:
  com.android.ide.common.process.ProcessException:
  java.util.concurrent.ExecutionException:
  java.lang.IllegalStateException: Multi dex requires Build Tools 21.0.0
  / Current: 19.1
  </code></pre>