Make starboard unit tests automatically resolve Frameworks.UWP package

Author: Jeyaram Jeyaraj

build/Tests/UnitTests/Starboard/Starboard.UnitTests.vcxproj

@@ -222,6 +222,9 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\..\..\..\tests\unittests\Starboard\LifetimeCounting.h" />
+  </ItemGroup>
+    <ItemGroup>
+    <PackageReference Include="WinObjC.Frameworks.UWP" Version="*" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <Import Project="$(StarboardBasePath)\common\winobjc.packagereference.override.targets" Condition="Exists('$(StarboardBasePath)\common\winobjc.packagereference.override.targets')"/>