An MSBuild target that adds RID-matching subvariants of source files to the compilation

RidItems.targets

<Project>
    <!-- This is a very simple version of what we'd actually want. We actually would need to:
       * get the target RID
       * get the OS portion of the RID graph _only_, no versions, no architectures
       * walk that graph in most-specific to least-specific order, including the first (most specific) items that match the expected pattern along the way 
       
       NOTE: .NET SDK Default Glob Include patterns wreck this entire feature -->
  <Target Name="ExpandRIDCompileItems" DependsOnTargets="AddImplicitDefineConstants" BeforeTargets="CoreCompile">
    <PropertyGroup>
      <RidDefines Condition="'$(RuntimeIdentifier)' != ''">$(RuntimeIdentifier.Split('-')[0])</RidDefines>
      <DefineConstants Condition="'$(RidDefines)' != ''">$(DefineConstants);$(RidDefines)</DefineConstants>
    </PropertyGroup>
    <ItemGroup>
      <_DefineItems Include="$(RidDefines)" />
      <_CompileFiles Include="@(_DefineItems)" CompileItemName="%(Compile.Filename)" CompileItemExtension="%(Compile.Filename)" Dir="%(Compile.RelativeDir)" Ext="%(Compile.Extension)" />
      <_RIDSpecificCompileItem Include="%(_CompileFiles.Dir)%(_CompileFiles.CompileItemName).%(_CompileFiles.Identity)%(_CompileFiles.Ext)">
        <DependentUpon>%(_CompileFiles.Dir)%(_CompileFiles.CompileItemName)%(_CompileFiles.Ext)</DependentUpon>
      </_RIDSpecificCompileItem>
     <Compile Include="@(_RIDSpecificCompileItem)" Condition="Exists(%(_RIDSpecificCompileItem.Identity))" />
    </ItemGroup>
  </Target>
</Project>
  
</Project>