csh: install hard link with same mode as target

Previously when using NO_ROOT we recorded METALOG entries for the /.cshrc
hard link with a different file mode than the link target, which is not
permitted.

We cannot just set LINKMODE here as it would also apply to the hard link
for the tcsh binary.

Reviewed by: brooks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D37499