Emulate _BitScanReverse64 on 32-bit MSVC targets
Emulate _BitScanReverse64 on 32-bit MSVC targets

_BitScanReverse64 is supported only on 64-bit Windows platforms, and cause build failure when compiling for 32-bit Windows.

PiperOrigin-RevId: 307128665

google/ruy,google/ruy,google/ruy,google/ruy