[llvm] ELFRelocs/AArch64: strip R_AARCH64_AUTH_RELATIVE, per doc (PR #86955)

[Daniil Kovalev via llvm-commits]

https://github.com/kovdan01 requested changes to this pull request.

The relocation is defined in https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst. The relocation is present in the spec (just not in the aaelf64 where you've tried to find it in but in pauthabielf64), we already use it in downstream and are submitting related patches to upstream - see, for example, #72714. Please don't delete it.

I suppose that @smithp35 can add something in terms of how Arm spec is organized, but basically I'm absolutely sure that the relocation is definitely needed. I see that there are other minor changes like changing comments in AArch64.def and adding a link to the aaelf64 spec - this might be useful, and, for example, a comment with a link to pauthabielf64 could be added.

Also tagging @asl 

https://github.com/llvm/llvm-project/pull/86955