cad/gmsh: Fix fetch
Add the distfile to LOCAL/zeising as well, since I did the update.
For some reason the distfile is notoriously hard to fetch from upstream, so
add a local copy of it as well.
From the buildlog:
=> Attempting to fetch http://gmsh.info/src/gmsh-4.6.0-source.tgz gmsh-4.6.0-source.tgz 11 MB 1542 Bps 02h10m fetch: transfer timed out fetch: gmsh-4.6.0-source.tgz appears to be truncated: 12047097/12048076 bytes => Attempting to fetch http://distcache.FreeBSD.org/ports-distfiles/gmsh/gmsh-4.6.0-source.tgz fetch: http://distcache.FreeBSD.org/ports-distfiles/gmsh/gmsh-4.6.0-source.tgz: size mismatch: expected 12048076, actual 12047097 => Couldn't fetch it - please try to retrieve this