[clang] [Offload] Always consider `flto` on for AMDGPU (PR #129118)

[Jan Patrick Lehr via cfe-commits]

jplehr wrote:

> I think people are just confusing what `-flto` means when put on a link job.

Including me. :)

Apologies for my ignorance, what does this do and why do we want it?
It allows for some (LTO-related?) flags to be forwarded/handled correctly?

https://github.com/llvm/llvm-project/pull/129118