Sync the startplasmacompositor with startkde
Summary: startplasma/startkde doesn't use qtpaths anymore.
Test Plan: starts wayland session
Reviewers: davidedmundson
Reviewed By: davidedmundson
Subscribers: davidedmundson, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D9795