Auto merge of #83260 - durin42:llvm-update, r=nagisa

Auto merge of #83260 - durin42:llvm-update, r=nagisa

rustc: changes to allow an llvm update

This lets LLVM be built using 2b5f3f446f36, which is only a few weeks old. The next change in LLVM (5de2d189e6ad) breaks rustc again by removing a function that's exposed into the Rust code, but I'll file a bug about that separately.

Please scrutinize the `thinLTOResolvePrevailingInIndex` call, as I'm not at all sure an empty config is right.

I'm also suspicious that a specific alignment could be specified in the call to CreateAtomicCmpXchg, but I don't know enough to figure that out.

Thanks!