fdo#81532 Handle symlinks to icon themes correctly

- added logging for icon theme scanning.

Change-Id: I799c5fc09879411020142f7808da0d9f2f63dc17
Reviewed-on: https://gerrit.libreoffice.org/10406
Tested-by: Rene Engelhard <rene@debian.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>