title: Unity3D and aar issue
body: <p>I have to build an aar module for Unity3D, but there are too many issues to do so.</p>
  
  <p>My working environment  </p>
  
  <blockquote>
    <p>Unity3D: 5.6.f1<br>
    Android Studio: 2.3.3<br>
    build tools: 25.0.2<br>
    SDK tool: 24.4</p>
  </blockquote>
  
  <p>I have built an aar file and unziped it to removed the <code>classes.jar</code> in <code>libs</code>, afterwards I copied the aar file and AndroidManifest.xml to <strong>asset\Plugins\Android</strong>. The package name of both, the android project and the unity project, are the same. </p>
  
  <p>Building the APK File afterwards, resulted in the following exception:</p>
  
  <pre><code>IOException: Failed to Move File / Directory from 'Temp/StagingArea/android-libraries/app-debug/classes.jar' to 'Temp/StagingArea/android-libraries/app-debug/libs/classes.jar'.
  UnityEditor.Android.PostProcessor.Tasks.ProcessAAR.Execute (UnityEditor.Android.PostProcessor.PostProcessorContext context)
  UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks (UnityEditor.Android.PostProcessor.PostProcessorContext context)
  UnityEditor.Android.PostProcessAndroidPlayer.PostProcess (BuildTarget target, System.String stagingAreaData, System.String stagingArea, System.String playerPackage, System.String installPath, System.String companyName, System.String productName, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry)
  UnityEditor.Android.AndroidBuildPostprocessor.PostProcess (BuildPostProcessArgs args)
  UnityEditor.PostprocessBuildPlayer.Postprocess (BuildTargetGroup targetGroup, BuildTarget target, System.String installPath, System.String companyName, System.String productName, Int32 width, Int32 height, System.String downloadWebplayerUrl, System.String manualDownloadWebplayerUrl, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.BuildReporting.BuildReport report) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:186)
  UnityEditor.HostView:OnGUI()
  </code></pre>
  
  <p>I've been looking for an answer for 3 days and I've tried everything I have found online, please help!</p>
  
  <p>I'm pretty sure there is nothing inside the aar files <code>libs</code> folder</p>