[llvm] [WebAssembly] Introduce CodeGenPassBuilder (PR #208983)

[Demetrius Kanios via llvm-commits]

QuantumSegfault wrote:

It's still experimental/WIP; I'm chipping away it. I'm not too far away from having something that can work for most programs on -O0 without much if any fallback (but we're still talking weeks or months at this rate... juggling many things).

Have to finish and merge what I still have open, then there's one major feature/PR to be done before it can mostly work, then it should just be lot's of little tweaks and incremental expansions (SIMD aside...)

https://github.com/llvm/llvm-project/pull/208983