[llvm] [PassBuilder] Add a pass to LTO postlink step (PR #124053)

[Paul Kirth via llvm-commits]

ilovepi wrote:

> llvm/docs/ReleaseNotes.md is the place to add release notes for pipeline changes
> 
> I think for the final commit to have the commit message/description, the PR's title and first comment must contain it, at least for squash and merge like LLVM does

Agreed that's a best practice, but I'm pretty sure if you're merging through github UI you can also edit the commit message and title before landing.

https://github.com/llvm/llvm-project/pull/124053