[llvm] [AArch64][NPM] Chalk out the CodeGenPassBuilder for NPM (PR #128471)

[Akshat Oke via llvm-commits]

optimisan wrote:

> We may need feedback from https://discourse.llvm.org/t/rfc-codegen-new-pass-manager-pipeline-construction-design/84659.

I believe it should be easy to swap out the current structure to the new one.
My main goal is to furnish the backend as soon as possible with passes ready to go in the NPM pipeline. I am refraining from spending too much time right now looking into the pipeline specifics and using what we already have, since you (mainly paperchalice and aebanks) are active on it.




https://github.com/llvm/llvm-project/pull/128471