[clang] [llvm] [X86][Driver] Do not add `-evex512` for `-march=native` when the target doesn't support AVX512 (PR #91694)

[Mike Lothian via cfe-commits]

FireBurn wrote:

@tstellar Can a note be added somewhere about this? Folks upgrading to llvm-18.1.6 will get errors unless they drop -march=native if they were on 18.1.5

https://github.com/llvm/llvm-project/pull/91694