Add a reference to the tracking bug for a workaround (#78582)

Author: jasonmalinowski

src/VisualStudio/Directory.Build.targets

@@ -2,6 +2,7 @@
 <Project>
   <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.targets', '$(MSBuildThisFileDirectory)../'))" />
 
+  <!-- Redefine _SetGeneratedOutputItems to work around https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems/edit/2471514/ -->
   <Target Name="_SetGeneratedOutputItems">
     <PropertyGroup>
       <!-- Changing VSExtensionOutputFolderPath will rename the .vsextension folder in the output directory,