games-roguelike/nethack: Bump to 3.6.1

games-roguelike/nethack: Bump to 3.6.1

* Bump to EAPI 7
* Update SRC_URI
* (Hopefully?) support prefix builds
* Various improvements suggested by mgorny
* Set SGID on the /var/games/nethack directory to avoid a potential
  privilege escalation during package upgrades
* Don't redefine LINUX and STATUS_HILITES
* Unconditionally enable DUMPLOG and SCORE_ON_BOTL per upstream
  recommendations
* Remove obsolete STATUS_VIA_WINDOWPORT and the now empty "experimental"
  USE flag

Thanks-to: Michał Górny <mgorny@gentoo.org>
Thanks-to: Laurent Bercot
Closes: https://github.com/gentoo/gentoo/pull/9661