Apparently we need to add a small delay after starting weston otherwise
it fails to connect on the CI system.
Additionally we switch to using headless-backend.so which should also
make the setup more robust.
Framework style build system which generates two libraries:
* KF5WaylandClient
* KF5WaylandServer
autotests are adjusted to compile again. They need to be changed to
use the libraries once the export header gets generated.