Makefile.inc1: Use ln -n instead of ln -h

We support both -h and -n, but GNU coreutils only supports -n,
so use that instead. This fixes the package build on Linux.

MFC after: 2 weeks
Reviewed by: (wosch, imp) (previous version), emaste
Better fix than the original patch suggested by: jrtc27
Sponsored by: https://www.patreon.com/bsdivy
Differential Revision: https://reviews.freebsd.org/D56656