[lld] [llvm] [lld][MachO] Add ARM64e pointer authentication linking support (PR #188378)

[Oliver Hunt via llvm-commits]

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ojhunt wrote:

Just verifying lld style allows auto instead of a named type? I'd certainly prefer a type here, but I don't know if it's _required_

Also verifying lowercase initial letter is correct naming style?

Both of these exist throughout this PR but I'll just comment/question here

https://github.com/llvm/llvm-project/pull/188378