[llvm] [LoongArch][GlobalISel] Adding initial GlobalISel infrastructure (PR #76912)

[Amara Emerson via llvm-commits]

https://github.com/aemerson commented:

Good to see another target adopting GISel 🙂

I'd recommend looking at what RISCV are also doing, in case there's common code for new targets that should be factored out.

https://github.com/llvm/llvm-project/pull/76912