Make sure that everything is buildable

samples/ControlCatalog.Android/ControlCatalog.Android.csproj

@@ -157,6 +157,11 @@
       <Name>ControlCatalog</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="System.Reactive">
+      <Version>3.1.1</Version>
+    </PackageReference>
+  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\Android\Xamarin.Android.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
      Other similar extension points exist, see Microsoft.Common.targets.

src/Skia/Avalonia.Skia.iOS/Avalonia.Skia.iOS.csproj

@@ -86,9 +86,6 @@
       <Name>Avalonia.Themes.Default</Name>
     </ProjectReference>
   </ItemGroup>
-  <ItemGroup>
-    <None Include="packages.config" />
-  </ItemGroup>
   <Import Project="..\Avalonia.Skia\Avalonia.Skia.projitems" Label="Shared" />
   <Import Project="..\..\Shared\RenderHelpers\RenderHelpers.projitems" Label="Shared" />
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\iOS\Xamarin.iOS.CSharp.targets" />