[clang] [llvm] UEFI backend for x86_64 (PR #109320)

[Tristan Ross via llvm-commits]

RossComputerGuy wrote:

Some of the clang changes seem kinda *odd*, maybe some of this work and #120632 could be conjoined? The LLVM stuff itself looks great, it's mainly the target stuff in clang seems odd to me.

https://github.com/llvm/llvm-project/pull/109320