Add dependency to Desktop native from C# test

Add a solution build dependency from the native Desktop project to the
C# test project, which currently assumes a Desktop x64 architecture for
lack of a better selection mechanism, so requires that DLL to be built
before starting to build `Microsoft.MixedReality.WebRTC.Tests`.

Author: jehumb-havok

Microsoft.MixedReality.WebRTC.sln

@@ -15,6 +15,9 @@ EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "Microsoft.MixedReality.WebRTC.Native.Win32", "libs\Microsoft.MixedReality.WebRTC.Native\src\win32\Microsoft.MixedReality.WebRTC.Native.Win32.vcxproj", "{928899BC-F131-4343-A1AB-72F3A5787E41}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.MixedReality.WebRTC.Tests", "tests\Microsoft.MixedReality.WebRTC.Tests\Microsoft.MixedReality.WebRTC.Tests.csproj", "{70AB2CE0-D35D-4911-AC83-545A611EA930}"
+	ProjectSection(ProjectDependencies) = postProject
+		{928899BC-F131-4343-A1AB-72F3A5787E41} = {928899BC-F131-4343-A1AB-72F3A5787E41}
+	EndProjectSection
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "Microsoft.MixedReality.WebRTC.Native.Tests", "libs\Microsoft.MixedReality.WebRTC.Native\test\Microsoft.MixedReality.WebRTC.Native.Tests.vcxproj", "{6D020425-2E3E-4BA7-BC46-00C8D29081C0}"
 	ProjectSection(ProjectDependencies) = postProject