Build on Gnu Hurd

Within Debian we created a patch to support build and use torsocks under Gnu Hurd. It would be nice if that patch would be part of upstream.

Unfortunately I cannot create a MR, as I don't have the permission to create a branch or a fork, so I simply have a patch. Author is Samuel. The patch is created on the released torsocks 2.5.0.

Gnu Hurd differences:

• No syscall system call.
• Uses __GNU__ preprocessor macro.
• Uses glibc like linux.

GnuHurd_torsocks_2.5.0.patch

More information you can find on Debian#767235.