[llvm] [AArch64] Handle inttoptr+add+ptrtoint pattern in lowerConstantPtrAuth (PR #189474)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

If we don't need it, I'd rather not set LookThroughIntToPtr to true, I think?  (The other change should ensure we don't miscompile.)

https://github.com/llvm/llvm-project/pull/189474