<AddinProject appVersion="4.0">
  <Project platforms="Mac Linux Win32">
    <AddinFile>GlassAddin/bin/Debug/GlassAddin.dll</AddinFile>
    <BuildFile>GlassAddin.sln</BuildFile>
    <BuildConfiguration>Debug</BuildConfiguration>
  </Project>
</AddinProject>
<AddinProject appVersion="4.0">
  <Project platforms="Mac Win32">
    <AddinFile>GlassAddin/bin/Debug/GlassAddin.dll</AddinFile>
    <BuildFile>GlassAddin.sln</BuildFile>
    <BuildConfiguration>Debug</BuildConfiguration>
  </Project>
</AddinProject>

Remove the Linux project platform
Remove the Linux project platform

Since Xamarin.Android only works with Mac and Windows