cmake: fix build with KWIN_BUILD_X11_BACKEND
It didn't build the windowed x11 backend before
(cherry picked from commit 4f2dcc33)
Co-authored-by: Xaver Hugl xaver.hugl@gmail.com
It didn't build the windowed x11 backend before
(cherry picked from commit 4f2dcc33)
Co-authored-by: Xaver Hugl xaver.hugl@gmail.com