[clang] [Driver][HIP] Bundle AMDGPU -S output under the new offload driver (PR #188262)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> This seems like we're _really_ stretching the new interface to match the old one. The goal is to support users manually modifying `.S` files and then passing it back into the compiler? I can see how that would be more difficult with the new interface. I'm not a huge fan of this, the expected behavior was that you get a `.S` that behaves like a valid host object.
> 
> I would greatly prefer a new, common interface that gave people the same flexibility rather than bolting more HIP specific handling onto this. But for the sake of expedience I could be talked into this.
> 
> Theoretically you could make it embed textual assembly in the section, but you'd need to put that in the filename when you send it back to `clang` through the linker wrapper. It would also look weird having a bunch of textual assembly in a global string in an assembly file.

The point of emitting .s file and then compile it to executable is to let users quickly inspect and tweak them. In that sense I think this is a useful feature that I think the new offload driver may consider to keep. Making .s file a binary format will defeat its purpose. However I do agree that we need better fit the feature into the structure of the new offload driver and I think we could refactor that later.

https://github.com/llvm/llvm-project/pull/188262