[llvm] [LTO] Add an option to select a pre-link pipeline (PR #82585)

[Nikita Popov via llvm-commits]

nikic wrote:

> > Couldn't this also be achieved by using something like `-opt-pipeline='thinlto-pre-link<O3>'`?
> 
> yes, although I'm not a huge fan of asking people to use the stringly typed interface (even though that's what the C API is to construct passes...)

I'd generally agree, but the use-case here sounds very exotic to me, quite far outside the usual LTO workflow. Seems like just the kind of situation that `-opt-pipeline` exists for.

https://github.com/llvm/llvm-project/pull/82585