[tests] There's no need to reference the MSBuild assemblies from Xamarin.MacDev.Tests anymore, we're going out-of-process!

tests/msbuild/Xamarin.MacDev.Tests/Xamarin.MacDev.Tests.csproj

@@ -7,24 +7,10 @@
     <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="Microsoft.Build" HintPath="$(MSBuildBinPath)\Microsoft.Build.dll" />
-    <Reference Include="Microsoft.Build.Framework" HintPath="$(MSBuildBinPath)\Microsoft.Build.Framework.dll" />
-    <Reference Include="Microsoft.Build.Tasks.Core" HintPath="$(MSBuildBinPath)\Microsoft.Build.Tasks.Core.dll" />
-    <Reference Include="Microsoft.Build.Utilities.Core" HintPath="$(MSBuildBinPath)\Microsoft.Build.Utilities.Core.dll" />
     <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit.ConsoleRunner" Version="3.11.1" />
     <PackageReference Include="NUnit.Extension.NUnitV2ResultWriter" Version="3.6.0" />
   </ItemGroup>
-  <ItemGroup>
-    <!-- Copy system Microsoft.Build*.dll and dependencies for tests to run against. We can remove this
-       and rely entirely on NuGet assets when mono/msbuild is merged into microsoft/msbuild. -->
-    <None Include="$(MSBuildToolsPath)\Microsoft.Build*.dll">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </None>
-    <None Include="$(MSBuildToolsPath)\System.*.dll">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </None>
-  </ItemGroup>
   <ItemGroup>
     <Compile Include="..\..\mtouch\Cache.cs">
       <Link>external\Cache.cs</Link>