After commit f4e15893e5be6da6c7642bb7ef9b14d5531afe41 (Bug 22516 - Ensure inotify fd is set close on exec) the code in bus/dir-watch-inotify.c is as follows:

#ifdef HAVE_INOTIFY_INIT1
     inotify_fd = inotify_init1 (IN_CLOEXEC);
#else
     inotify_fd = inotify_init ();
#endif
     if (inotify_fd <= 0) {
      _dbus_warn ("Cannot initialize inotify\n");
      goto out;
     } 

This does break when compiling with a recent userspace and then using an older kernel.

The fix from https://bugzilla.gnome.org/show_bug.cgi?id=593775 (same bug in glib) can also be used here.