title: Xamarin Build fails at aapt (attribute *** allready defined)
body: <p>We have CI server for nightly builds. We have also the required dependencies on the build server for our xamarin builds. For some reason, somthing this week changed (I dont know what) but now in the _UpdateAndroidResgen build step aapt is getting attributes defined twice which causes the build to fail for some reason. </p>
  
  <p><code>Failed to generate resource table for split ''
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "navigationMode" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:73: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "displayOptions" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:73: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "actionBarSize" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:82: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "buttonTintMode" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:84: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "showDividers" already defined with incompatible format.
  [20:53:33]  nothing matches overlay file notification_media_action.xml, for flavor v11
  [20:53:33]  nothing matches overlay file notification_media_cancel_action.xml, for flavor v11
  [20:53:33]  nothing matches overlay file notification_template_big_media.xml, for flavor v11
  [20:53:33]  nothing matches overlay file notification_template_big_media_narrow.xml, for flavor v11
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:86: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "showAsAction" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:90: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.v7.AppCompat\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "backgroundTintMode" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\8D3A6302159015EB54DABA3378105A95\res\values\values.xml:100: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "layout_scrollFlags" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:14: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "collapsedTitleGravity" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:17: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "expandedTitleGravity" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:17: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "layout_collapseMode" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:16: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "layout_anchorGravity" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:19: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "fabSize" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:21: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "tabMode" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:28: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: Attribute "tabGravity" already defined with incompatible format.
  [20:53:33]  ~\obj\x64\Release\resourcecache\1E8DAFD410D28824E5C274B16FD597B6\res\values\values.xml:28: Original attribute defined here.
  [20:53:33]  ~\obj\x64\Release\__library_projects__\Xamarin.Android.Support.Design\library_project_imports\res\values\values.xml(2, 0): error APT0000: String types not allowed (at 'fabSize' with value 'auto').
  [20:53:33]<br>
  [20:53:33]  The command exited with code 1.
  </code></p>
  
  <p>I have verified that the problem seems to be on the build runner as the same code which was passing 4 days ago is now failing with the aapt error as well. Also verified the android sdk and build tools versions are the same as they have always been. I have tried reverting, deleting all bin and obj folders as well as the xamarin cache folder ~\AppData\Local\Xamarin\ I have also reinstalled the android build tools. Really quite stumped at this point.</p>
  
  <p>Has anyone seen this issue before?</p>