[clang] [flang] [clang] Add option to specify opt pipeline during offload lto (PR #114401)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> For the purposes of experimentation, `-Xoffload-linker` is sufficient that this change is not necessary.

Also worth noting that `-Xoffload-linker-amdgcn-amd-amdhsa` should work if you just want to target a single toolchain.

https://github.com/llvm/llvm-project/pull/114401