Fix duplicate types in ports on desktop

Author: ericstj

pkg/test/packageSettings/System.IO.Ports/net/ignoreTypes.targets

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <BuildConfigurations>
       netstandard;
+      netfx;
     </BuildConfigurations>
   </PropertyGroup>
 </Project>

src/System.IO.Ports/ref/Configurations.props

@@ -3,12 +3,18 @@
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
   <PropertyGroup>
     <ProjectGuid>{75DE4259-43BB-4067-9F30-3AC920D51AEC}</ProjectGuid>
+    <IsPartialFacadeAssembly Condition="'$(TargetGroup)' == 'netfx'">true</IsPartialFacadeAssembly>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Release|AnyCPU'" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netfx-Debug|AnyCPU'" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netfx-Release|AnyCPU'" />
   <ItemGroup>
     <Compile Include="System.IO.Ports.cs" />
-    <Reference Include="netstandard" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetGroup)' == 'netfx'">
+     <Reference Include="mscorlib" />
+     <Reference Include="System" />
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
 </Project>