title: Android: set sdk.dir in local.properties to ANDROID_HOME environment variable
body: <p>So the <code>local.properties</code> file holds the reference to the Android SDK directory in <code>sdk.dir</code> variable. For me it is <code>sdk.dir=/Users/rajkiran/Library/Android/sdk</code>. On my CI machine, the <code>sdk.dir</code> refers to the SDK directory which points to an invalid location since the username is different. </p>
  
  <p>Is there any way so that I can set SDK directory as my <code>ANDROID_HOME</code>?</p>
  
  <p>Perhaps something like this: <code>sdk.dir=$ANDROID_HOME</code>, so that on my CI machine, it will set the SDK directory from the environment variable?</p>