[lld] [lld][AArch64][ELF][PAC] Support AUTH relocations and AUTH ELF marking (PR #72714)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay requested changes to this pull request.

Apologies for the delay. With the switch to GitHub it's kinda difficult to find review requests that need my attention...

Is there a dynamic loader implementation? Without it it's difficult to verify the correctness.

For my RISC-V TLSDESC changes I have musl to verify the correctness.

https://github.com/llvm/llvm-project/pull/72714