You have to remove the trailing slashes in the preinst.
$ file /usr/share/doc/skype /usr/share/doc/skype: symbolic link to `skype-common'
$ file /usr/share/doc/skype/ /usr/share/doc/skype/: directory
You have to remove the trailing slashes in the preinst.
$ file /usr/share/ doc/skype doc/skype: symbolic link to `skype-common'
/usr/share/
$ file /usr/share/ doc/skype/ doc/skype/ : directory
/usr/share/