This flag originally controlled only whether hardware accelerated CRC32 was done on s390x, but as of WT-4198 and SERVER-36301, the flag actually has wider reaching effects, and disables hardware CRC32 on all platforms:

See https://github.com/mongodb/mongo/commit/2be874cd1608b343233fbcf5aafb3b759d75c5d6

The flag should be renamed to something like --use-hardware-crc32

This change should likely be backported to 4.0, since SERVER-36301 should be backported to 4.0.