VirtualBox has problems with hard links in shared folders, leading to NetHack dying when /data is a host folder mounted via docker-machine.  Thus, no more hard links.
VirtualBox has problems with hard links in shared folders, leading to NetHack
dying when /data is a host folder mounted via docker-machine.  Thus, no more
hard links.

References:
  <https://github.com/docker/machine/issues/1876>
  <https://www.virtualbox.org/ticket/818>

jwodder/nethack-docker