xwayland: "EGL_EXT_device_base" required for EGLStream

eglQueryDevicesEXT() would abort if the required extensions are not
available, meaning that enabling “-eglstream” on a non-EGLStream
capable hardware would lead to an abort().

Check that "EGL_EXT_device_base" extension is available and bail out
early if not, so we don't abort() later in eglQueryDevicesEXT().

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

hw/xwayland/xwayland-glamor.c

@@ -67,6 +67,9 @@ xwl_glamor_egl_get_devices(int *num_devices)
     int drm_dev_count = 0;
     int i;
 
+    if (!xwl_glamor_egl_supports_device_probing())
+        return NULL;
+
     /* Get the number of devices */
     ret = eglQueryDevicesEXT(0, NULL, num_devices);
     if (!ret || *num_devices < 1)