title: What causes the "ConvertResourcesCases" failed unexpectedly?
body: <p>did anyone facing this kind of problem too? It happened when I upgrade Xamarin to current version. Already check at xamarin forum, still zero answer. 
  Thanks.</p>
  
  <blockquote>
    <p>C:\Program Files
    (x86)\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2,2):
    Error MSB4018: The "ConvertResourcesCases" task failed unexpectedly.
    System.UnauthorizedAccessException: Access to the path
    'obj\Debug\res\values\strings.xml' is denied.    at
    System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)<br>
    at System.IO.File.InternalCopy(String sourceFileName, String
    destFileName, Boolean overwrite, Boolean checkHost)    at
    System.IO.File.Copy(String sourceFileName, String destFileName,
    Boolean overwrite)    at
    Xamarin.Android.Tools.Files.CopyIfChanged(String source, String
    destination)    at
    Xamarin.Android.Tasks.ConvertResourcesCases.FixupResources(ITaskItem
    item, Dictionary<code>2 acwMap)    at
    Xamarin.Android.Tasks.ConvertResourcesCases.FixupResources(Dictionary</code>2
    acwMap)    at Xamarin.Android.Tasks.ConvertResourcesCases.Execute()<br>
    at
    Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
    at
    Microsoft.Build.BackEnd.TaskBuilder.d__20.MoveNext()
    (MSB4018) (Gcm.Client)</p>
  </blockquote>