Prevent rebuild of TestAppUWP on no updates (#112)

Author: fiban-havok

examples/TestAppUwp/Directory.Build.props

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\Directory.Build.props" />
+  <PropertyGroup>
+    <!-- This project (UWP) references Microsoft.MixedReality.WebRTC.dll (.NET Standard) which is output in a different directory. -->
+	<!-- Set this to false so that it is copied to this project's output directory, otherwise it will force a new build every time. -->
+    <UseCommonOutputDirectory>False</UseCommonOutputDirectory>
+  </PropertyGroup>
+</Project>