x11-wm/plasma5-kwin: unbreak with libglvnd >= 1.3.4

src/plugins/platforms/x11/common/eglonxbackend.cpp:227:66: error: cannot initialize a parameter of type 'EGLNativeWindowType' (aka 'void *') with an lvalue of type 'xcb_window_t' (aka 'unsigned int')

surface = eglCreateWindowSurface(eglDisplay(), config(), window, nullptr);
                                                         ^~~~~~

PR: 258269
Reported by: antoine (via exp-run)
See also: https://bugs.gentoo.org/810511