if no xcursor is found, don't build the kcm at all
Summary:
the code path of kcm without xcursors was broken since over a year,
meaning is not tested at all and can't be guaranteed to be supported
Test Plan: ino build error when xcursor is not found
Reviewers: Plasma, apol
Reviewed By: apol
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D20375