title: ant debug, and sdk.dir
body: <p>I have a problem to generate the Android APK file.</p>
  
  <p>When I run <code>ant debug</code> compilation work fine, but when I run <code>ant debug</code></p>
  
  <p>I have following error:</p>
  
  <pre><code>iMac:proj.android smartmind$ ant debug
  Buildfile: /Users/smartmind/Works/Smallthing/cocos2d-x/samples/HelloCpp/proj.android/build.xml
  
  BUILD FAILED
  /Users/smartmind/Works/Smallthing/cocos2d-x/samples/HelloCpp/proj.android/build.xml:46: sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through an env var
  
  Total time: 0 seconds
  </code></pre>
  
  <p>I don't know what is problem.</p>