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

[Arthur Eubanks via llvm-commits]

aeubanks 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

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