Add aarch64 version of crc::checksum_long

This adds support for aarch64 (at least -march=armv8-a+crc or -march=armv8.1-a) in crc::checksum_long.

Note: the test build was achieved following the instructions at https://codimd.web.cern.ch/s/G2qnvDjev

/cc @bcouturi @valassi