Restore handling of __PassThroughArg for `--`
Restore handling of __PassThroughArg for `--`

cshung/coreclr,poizan42/coreclr,cshung/coreclr,cshung/coreclr,krk/coreclr,krk/coreclr,krk/coreclr,krk/coreclr,wtgodbe/coreclr,cshung/coreclr,poizan42/coreclr,poizan42/coreclr,wtgodbe/coreclr,cshung/coreclr,mmitche/coreclr,cshung/coreclr,krk/coreclr,mmitche/coreclr,poizan42/coreclr,mmitche/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,mmitche/coreclr,mmitche/coreclr,poizan42/coreclr,krk/coreclr,wtgodbe/coreclr,mmitche/coreclr,wtgodbe/coreclr,poizan42/coreclr