title: Can't build Xamarin Forms, Android project, TargetFrameworkVersion v9.0 not is not supported
body: <p>Trying to build a Xamarin Forms Android project.  The Minimum Android Version and Target Android Version are set to "Android 8.1 (Api Level 27 - Oreo) in the project Properties. </p>
  
  <p>Under the SDK Manager, I have API Level Versions (SDK Platforms) 21-28 installed. </p>
  
  <p>When loading the project, I get the following error: </p>
  
  <p>Severity    Code    Description Project File    Line    Suppression State
  Error       Project MyProjMobile.Android cannot build using TargetFrameworkVersion v9.0 because it s not supported. Please change your Xamarin.Android project to target an API version that is supported.          0   </p>
  
  <p>No matter what I set the TargetFramwork settings to (I tried lowering them), I continue to get the same error. </p>
  
  <p>I have even tried loading this project after deleting the bin, obj and packages folders with no luck. </p>
  
  <p>You can look at my manifest here: </p>
  
  <p><a href="https://www.dropbox.com/s/7dnp6qqknbbn5ee/AndroidManifest.xml?dl=0" rel="nofollow noreferrer">https://www.dropbox.com/s/7dnp6qqknbbn5ee/AndroidManifest.xml?dl=0</a></p>
  
  <p>Any ideas? </p>