cad/kicad: use GNU tar for building resources/images.tar.gz

This is a prerequisite for having reproducible package builds:
the archive would have to be the same across builds, and we get
that by setting all file timestamps inside the archive to a fixed
value (the epoch, typically) or removing the timestamps alltogether,
if possible (atime and ctime).
Doing this requires GNU tar, as the neccessary extensions are not
available in FreeBSD's base system tar.
The only affected file in this package is share/kicad/resources/images.tar.gz.

PR: 291905
Differential Revision: https://reviews.freebsd.org/D57069
Reported by: cen