[clang] [llvm] Add support for Arm Cortex A78AE CPU (PR #84485)

[Jonathan Thackray via cfe-commits]

jthackray wrote:

> Also does this address the -mcpu=native part of #84450 as well?

I've added a host id (0xd42) to llvm/lib/TargetParser/Host.cpp, so I think so (unless there's something else required).

https://github.com/llvm/llvm-project/pull/84485