Tracking issue for "Create safe LLVM bindings"

[Centril]

Refiling rust-lang/rfcs#644 here.

rustc's LLVM bindings are a bit of a hodgepodge. Some abstractions have been added on top of the C bindings, but not consistently. It would be nice to do some serious cleanup here so that rustc is using only safe, high-level bindings.

cc #52461

[tbu-]

#8274

[IsaacWoods]

I wonder if we could take some inspiration from Inkwell, which already aims to safely wrap llvm-sys

[Centril]

Nothing has happened here for over a year so I think the issue doesn't carry it's weight.