[main] Source code updates from dotnet/dotnet#500

dotnet-maestro[bot] merged 3 commits intomaindotnet/source-build-externals:mainfrom

darc-main-cd285c3b-16bc-444e-bdad-dbf5a61dd9e9dotnet/source-build-externals:darc-main-cd285c3b-16bc-444e-bdad-dbf5a61dd9e9Copy head branch name to clipboard