Tentative fix for transient missing UnoViewGroup build error (#971)

Tentative fix for transient missing UnoViewGroup build error

Author: ghuntley

src/Uno.UI.BindingHelper.Android/Uno.UI.BindingHelper.Android.csproj

@@ -55,7 +55,7 @@
 
 	<Import Project="..\Uno.CrossTargetting.props" />
 
-	<Target Name="_CompileUnoJavaCreateOutputs">
+	<Target Name="_CompileUnoJavaCreateOutputs" BeforeTargets="Build">
 		<!-- 
 		Create the EmbeddedJar itemgroup here so the Xamarin tooling picks it up, 
 		but in the obj folder so we dont have rebuild and git ignore issues.