Fix references with .NET 6.x and above

Author: lukespragg

netfx.props

@@ -21,11 +21,12 @@
     <FrameworkPathOverride Condition="'$(BaseFrameworkPathOverrideForMono)' != '' AND '$(TargetFramework)' == 'net471'">$(BaseFrameworkPathOverrideForMono)/4.7.1-api</FrameworkPathOverride>
     <EnableFrameworkPathOverride Condition="'$(BaseFrameworkPathOverrideForMono)' != ''">True</EnableFrameworkPathOverride>
 
-    <!-- Workaround for targeting .NET 3.5 with dotnet CLI https://github.com/Microsoft/msbuild/issues/1333#issuecomment-296346352 -->
-    <FrameworkPathOverride Condition="'$(TargetFramework)' == 'net35' AND '$(OS)' == 'Windows_NT'">C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v3.5\Profile\Client</FrameworkPathOverride>
-    <FrameworkPathOverride Condition="'$(TargetFramework)' == 'net35' AND '$(OS)' == 'OSX'">/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/2.0-api</FrameworkPathOverride>
-
     <!-- Add the Facades directory. Not sure how else to do this. Necessary at least for .NET 4.5 -->
     <AssemblySearchPaths Condition="'$(BaseFrameworkPathOverrideForMono)' != ''">$(FrameworkPathOverride)/Facades;$(AssemblySearchPaths)</AssemblySearchPaths>
   </PropertyGroup>
+
+  <!-- Add reference assemblies for use when building with .NET 6.x and above -->
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" PrivateAssets="All" />
+  </ItemGroup>
 </Project>