title: Error: The prefix "tools" for attribute "tools:overrideLibrary" associated with an element type "uses-sdk" is not bound
body: <p>I got the following error while build apk file from unity on mac osx sierra. this also build fine before I reboot my macbook, but not now.</p>
  
  <p>I've added error details below:</p>
  
  <p>Note: I'm using facebook sdk.</p>
  
  <pre><code>Error: Error while saving blame file, build will continue
  Error: The prefix "tools" for attribute "tools:overrideLibrary" associated with an element type "uses-sdk" is not bound.
  
  UnityEditor.HostView:OnGUI()
  </code></pre>
  
  <p>and:</p>
  
  <pre><code>AndroidSDKToolsException: Unable to merge android manifests. See the Console for more details. 
  UnityEditor.Android.AndroidSDKTools.DetectErrorsAndWarnings (System.String logMessages, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.RunCommandInternal (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.RunCommandSafe (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.RunCommand (System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.RunCommand (System.String[] sdkToolCommand, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.RunCommand (System.String[] sdkToolCommand, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
  UnityEditor.Android.AndroidSDKTools.MergeManifests (System.String target, System.String mainManifest, System.String[] libraryManifests, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit)
  UnityEditor.Android.PostProcessor.Tasks.GenerateManifest.MergeManifests (UnityEditor.Android.PostProcessor.PostProcessorContext context, System.String targetManifest, System.String mainManifest)
  UnityEditor.Android.PostProcessor.Tasks.GenerateManifest.Execute (UnityEditor.Android.PostProcessor.PostProcessorContext context)
  UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks (UnityEditor.Android.PostProcessor.PostProcessorContext context)
  UnityEditor.HostView:OnGUI()
  </code></pre>
  
  <p>last</p>
  
  <pre><code>UnityEditor.BuildPlayerWindow+BuildMethodException: Build failed with errors.
    at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x001b9] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:162 
    at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00050] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:83 
  UnityEditor.HostView:OnGUI()
  </code></pre>