Trimming issue workaround in .NET 8 (#2022)

Author: JamesNK

Directory.Build.targets

@@ -30,4 +30,19 @@
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="$(MicrosoftSourceLinkGitHubPackageVersion)" PrivateAssets="All" />
   </ItemGroup>
 
+  <!-- 
+    Make a netstandard2.1 copy of the .net ILLinkPack to work around a trimming issue.
+    See https://github.com/dotnet/linker/issues/3175
+    TODO: Remove once .NET 8 + trimming + netstandard2.1 is fixed.
+  -->
+  <Target Name="_FixKnownILLinkPack"
+          BeforeTargets="ProcessFrameworkReferences">
+    <ItemGroup>
+      <KnownILLinkPack Include="@(KnownILLinkPack)"
+                       Condition="'%(TargetFramework)' == 'net8.0'"
+                       TargetFramework="netstandard2.1"
+                       ILLinkPackVersion="%(KnownILLinkPack.ILLinkPackVersion)" />
+    </ItemGroup>
+  </Target>
+
 </Project>