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

[Daniel Rodríguez Troitiño via llvm-commits]

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drodriguez wrote:

No need for something like this this in the `else` branch below? (non-extern `relocation_info`)

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