Build Fails on Each Run
<p>I have already installed Android SDK Platform 19</p>

<p>Warning:Project is building density based multiple APKs but using tools version 19, you should upgrade to build-tools 21 or above to ensure proper packaging of resources.</p>

<p>:app:processDebugResources FAILED</p>

<p>Error:Execution failed for task ':app:processDebugResources'.</p>

<blockquote>
  <p>com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/home/sneha/Android/Sdk/build-tools/19.1.0/aapt'' finished with non-zero exit value 1</p>
</blockquote>