[llvm] [NVPTX] fix ptxas tests introduced by #124865 (PR #125927)

[Akshay Deodhar via llvm-commits]

akshayrdeodhar wrote:

Thanks for this- I have _not_ run the ptxas-verify checks on this 🙂 , and sort of followed whatever I saw in older files. Upon setting `LLVM_PTXAS_EXECUTABLE`, this became apparent, and the version/arch changes in this MR fixes those problems. 

LGTM!

https://github.com/llvm/llvm-project/pull/125927