Enable android nuget build

dirs.proj

@@ -9,11 +9,6 @@
     <ProjectReference Remove="src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github/**/*.*proj" />
     <ProjectReference Remove="tests/Avalonia.ReactiveUI.Events.UnitTests/Avalonia.ReactiveUI.Events.UnitTests.csproj" />
   </ItemGroup>
-  <!--<ItemGroup Condition="!Exists('$(MSBuildExtensionsPath)\Xamarin\Android')">-->
-  <ItemGroup>
-    <ProjectReference Remove="src/Android/**/*.*proj" />
-    <ProjectReference Remove="samples/ControlCatalog.Android/ControlCatalog.Android.csproj" />
-  </ItemGroup>
   <ItemGroup Condition="!Exists('$(MSBuildExtensionsPath)\Xamarin\iOS')">
     <ProjectReference Remove="src/iOS/**/*.*proj" />
     <ProjectReference Remove="samples/ControlCatalog.iOS/ControlCatalog.iOS.csproj" />
@@ -23,6 +18,11 @@
     <ProjectReference Remove="samples/interop/**/*.*proj" />
     <ProjectReference Remove="samples/ControlCatalog.Desktop/*.*proj" />
   </ItemGroup>
+  <!-- Build android projects only on Windows, where we have installed android workload -->
+  <ItemGroup Condition="!$([MSBuild]::IsOsPlatform('Windows'))">
+    <ProjectReference Remove="src/Android/**/*.*proj" />
+    <ProjectReference Remove="samples/ControlCatalog.Android/ControlCatalog.Android.csproj" />
+  </ItemGroup>
 
   <ItemGroup>
     <PackageReference Include="SlnGen" Version="2.0.40" PrivateAssets="all" />