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

[Fangrui Song via llvm-commits]

MaskRay wrote:

*[`lld/test/ELF/aarch64-reloc-pauth.s` line 65 at r9](https://reviewable.io/reviews/llvm/llvm-project/72714#-Nr30FUWEe4tRgXhAAwz:-Nr30FUWEe4tRgXhAAx-:bbqtlis) ([raw file](https://github.com/llvm/llvm-project/blob/ec1c6322341f3f25f3ad0070810c4a90d188c3b5/lld/test/ELF/aarch64-reloc-pauth.s#L65)):*
> ```gas
> # RELR-NEXT: }
> 
> # RUN: llvm-readobj -x .test %t2 | FileCheck --check-prefix=HEX %s
> ```

You can run `-r -x .test` in one invocation to save one llvm-readobj command.


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