[llvm] [PAC][ELF] Place AUTH constants in .data.rel.ro for position dependent code (PR #150418)

[Anatoly Trosinenko via llvm-commits]

https://github.com/atrosinenko commented:

Added a couple nit-picky comments. This looks good to me now, though I'm not an expert in the nuances of ELF emission.

https://github.com/llvm/llvm-project/pull/150418