[clang] [HIP] change default offload archs (PR #139281)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> spir-v would probably be an OK alternative. It's not great (probably leases some performance on the table vs the native build), but the binary will presumably work on other machines.

I'd probably go with just error and emit nothing, but I'm sure that will break someone's build somewhere 



https://github.com/llvm/llvm-project/pull/139281