We have lots of inconsistency at the moment in CMakeLists.txt files. Most
of it is due to kwin being a very old project. This change hopefully fixes
all of it.
Summary: it's a smaller library and provides everything we need
Test Plan: Compiles
Reviewers: apol
Reviewed By: apol
Subscribers: kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D19061