[llvm] [Github] Match backend:NVPTX files outside llvm/ (PR #221968)

[Erich Keane via llvm-commits]

https://github.com/erichkeane commented:

I have no idea about this, so I don't know how to review this... but could/should we instead 'add' the clangir directories here? 

https://github.com/llvm/llvm-project/pull/221968