Enable building on GNU/Hurd platforms

[ellert]

Checklist

• Pull request details were added to CHANGELOG.rst
• Documentation was updated (if needed)

[rhpvorderman]

Thanks for enable builds on GNU/Hurd. I cannot give any impression that I will support GNU/Hurd builds however. People who try that are on their own. (Although I'd imagine they'd be quite capable to fix any issues themselves given that they run GNU Hurd!)

[rhpvorderman]

Awesome. Thanks!