[libc-commits] [libc] [libc][__support][bit] Switch popcount to Brian Kernighan’s Algorithm (PR #95625)

[Ryan Beltran via libc-commits]

rpbeltran wrote:

I believe the [relevant tests](https://github.com/llvm/llvm-project/blob/cfbed2c0e6110878e6174067e2fb8013fc512620/libc/test/src/__support/CPP/bit_test.cpp#L224-L229) are likely just using the builtin when ran, but I manually validated by disabling that guard locally and telling it to always use this code.

Not sure what the better way would be to add a testcase that never uses builtins.

https://github.com/llvm/llvm-project/pull/95625