[XamlC] change module MVID (#1045)

Author: StephaneDelcroix

Xamarin.Forms.Build.Tasks/XamlCTask.cs

@@ -204,6 +204,11 @@ public override bool Execute(out IList<Exception> thrownExceptions)
 #pragma warning restore 0618
 						resourcesToPrune.Add(resource);
 					}
+					if (hasCompiledXamlResources) {
+						Logger.LogString(2, "  Changing the module MVID...");
+						module.Mvid = Guid.NewGuid();
+						Logger.LogLine(2, "done.");
+					}
 					if (!KeepXamlResources) {
 						if (resourcesToPrune.Any())
 							Logger.LogLine(2, "  Removing compiled xaml resources");