Add fix for big-endian platforms (Closes: #85)

[guimard]

This fixes #85

[guimard]

Thank you, @guimard, for this patch! \o/

However, this still doesn't resolve the s390x failure completely; see the following logs: https://autopkgtest.ubuntu.com/results/autopkgtest-jammy/jammy/s390x/n/node-pbkdf2/20220120_013605_914b3@/log.gz

Let me know what you think?

Fixed now

[utkarsh2102]

All tests pass on all architectures now. Thank you very much!