[llvm] Enable logf128 constant folding for AArch64 (PR #96287)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I'd still prefer to use some sort of detection. If you can't figure out a way to do it in the header itself, please use CMake tests.

https://github.com/llvm/llvm-project/pull/96287