localedef: Handle symbolic links when generating locale-archive

Whenever locale data for any locale included symbolic links, localedef
would throw the error "incomplete set of locale files" and exclude it
from the generated locale archive.  This commit fixes that.

Co-authored-by: Florian Weimer <fweimer@redhat.com>

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit ea89d5bb)