[clang] [HIP] Pass `-O0` by default for HIP no-RDC compilations (PR #211790)

[Matt Arsenault via cfe-commits]

https://github.com/arsenm commented:

Isn't this what you get by not passing -O0? I'd rather take the no-opts by default than explicitly using -O0 

https://github.com/llvm/llvm-project/pull/211790