[libcxx-commits] [libcxx] Replace uses of `__libcpp_ctz` by `__countr_zero` (PR #132639)

[Mark de Wever via libcxx-commits]

mordante wrote:

> Hi @mordante, thank you for the update on the current status of removing Clang 18 support, which is currently blocked by some CI runners. I understand that the changes in this patch will need to be put on hold until Clang 18 support is officially dropped (@PaulXiCao).

Looking at the status of the CI this works in Clang-18; the ARM runners are still on Clang-18. 

https://github.com/llvm/llvm-project/pull/132639