[llvm] [AArch64] emitAddress: Handle signed GOT. (PR #172926)

[Harald van Dijk via llvm-commits]

hvdijk wrote:

> I'd like to actually ask if the motivation for this PR from its description is relevant at the moment.

Yes. The linker error was the result of two different problems combined:

- `aarch64-linux-pauthtest` was wrongly picked up as supporting both PAuth relocations and IFUNCs.
- Targets supporting both PAuth relocations and IFUNCs were not handled correctly and would result in that linker error.

#171648 addressed the first problem, this PR addresses the second problem. Addressing the first problem meant that the second problem turned almost purely theoretical, as no current target supports both PAuth relocations and IFUNCs, but as had been requested, since it was an easy enough change, I put it up anyway. If someone does end up working on a target that supports both, they will end up getting this linker error again, and this PR will hopefully be easy enough to find even we end up not merging it.

https://github.com/llvm/llvm-project/pull/172926