[clang] [Clang][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (2/3) (PR #125688)

[Csanád Hajdú via cfe-commits]

Il-Capitano wrote:

I've rebased this patch onto main, since https://github.com/llvm/llvm-project/pull/125687 has been merged, so it's now ready for review.

https://github.com/llvm/llvm-project/pull/125688