RE: Use __attribute__((target(sse4.2))) for SSE42 CRC32C

> I believe we expect MSVC builds to use meson at this point, which is probably
> why there's this extra check:
>
>   if cc.get_id() == 'msvc'
>     cdata.set('USE_SSE42_CRC32C', false)
>     cdata.set('USE_SSE42_CRC32C_WITH_RUNTIME_CHECK', 1)
>     have_optimized_crc = true
>

Ah, I missed this. This makes sense.