Backport pipeline changes (dotnet/core-setup#8780)

Backport pipeline changes (dotnet/core-setup#8780)

* Backport changes to get CI working in runtime repository.

* /root/coresetup->/root/runtime

* Delete broken RPM symlink that might still be around if the RPM packaging job failed.

* Add back old Documentation folder excludes with a more specific include for the manpages folder.

* Try other variable format for template path.

* Treat subsetArg as a parameter with a default value instead of as a variable.

* Pass subset arg to template.

* Try other variable format.

* Try another variant.

* Switch back variable format now that I got a different (seemingly actionable) error.

* Fix passing the subset arg.

Commit migrated from https://github.com/dotnet/core-setup/commit/9e6766a796d47c3678adf6e0c9bfa3e8b070be75