compositor-drm, compositor-fbdev: stop suggesting root

Stop suggesting to run Weston as root, it is only meant for debugging.
Instead, mention the two supported ways to run Weston on DRM and fbdev:
weston-launch helper and logind service.

Cc: "Ucan, Emre (ADITG/ESB)" <eucan@de.adit-jv.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
[Pekka: added forgotten "using" word.]

libweston/compositor-drm.c

@@ -4039,8 +4039,9 @@ drm_backend_create(struct weston_compositor *compositor,
 	compositor->launcher = weston_launcher_connect(compositor, config->tty,
 						       seat_id, true);
 	if (compositor->launcher == NULL) {
-		weston_log("fatal: drm backend should be run "
-			   "using weston-launch binary or as root\n");
+		weston_log("fatal: drm backend should be run using "
+			   "weston-launch binary, or your system should "
+			   "provide the logind D-Bus API.\n");
 		goto err_compositor;
 	}
 

libweston/compositor-fbdev.c

@@ -736,8 +736,9 @@ fbdev_backend_create(struct weston_compositor *compositor,
 	compositor->launcher =
 		weston_launcher_connect(compositor, param->tty, "seat0", false);
 	if (!compositor->launcher) {
-		weston_log("fatal: fbdev backend should be run "
-			   "using weston-launch binary or as root\n");
+		weston_log("fatal: fbdev backend should be run using "
+			   "weston-launch binary, or your system should "
+			   "provide the logind D-Bus API.\n");
 		goto out_udev;
 	}