tests: Start dbus-monitor for the portal tests if required

Same as in the pytest suite, start dbus-monitor on our test session bus
if XDP_DBUS_MONITOR is set in the environment.

tests/test-portals.c

@@ -173,6 +173,20 @@ global_setup (void)
  session_bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
  g_assert_no_error (error);
 
+ if (g_getenv ("XDP_DBUS_MONITOR"))
+ {
+ launcher = g_subprocess_launcher_new (G_SUBPROCESS_FLAGS_NONE);
+ g_subprocess_launcher_setenv (launcher, "DBUS_SESSION_BUS_ADDRESS", g_test_dbus_get_bus_address (dbus), TRUE);
+ g_subprocess_launcher_take_stdout_fd (launcher, xdup (STDERR_FILENO));
+ argv[0] = "dbus-monitor";
+ argv[1] = NULL;
+ subprocess = g_subprocess_launcher_spawnv (launcher, argv, &error);
+ g_assert_no_error (error);
+ g_test_message ("Launched %s with pid %s\n", argv[0],
+ g_subprocess_get_identifier (subprocess));
+ test_procs = g_list_append (test_procs, g_steal_pointer (&subprocess));
+ }
+
  /* start portal backends */
  name_appeared = FALSE;
  watch = g_bus_watch_name_on_connection (session_bus,