title: Gradle ADT 0.4 error: android.buildToolsVersion is missing
body: <p>Attempting to build my Android project using the latest ADT tools release of Gradle, I get the following error:</p>
  
  <pre><code>Execution failed for task ':compileDebugAidl'.
  &gt; android.buildToolsVersion is missing!
  </code></pre>
  
  <p>Using Gradle 1.6, Android plugin 0.4.</p>