message: qt5: Fix MOC dependency retrieval.
diff: @@ -354,11 +354,12 @@ def deps_handler(builder, path_obj, t):
  'drake.cxx.qt',
  drake.log.LogLevel.debug,
  '%s: retrieve reference to MOC %s', builder, path_obj):
  - source = drake.node(drake.Path(path_obj).with_extension('moc.hh'))
  + header = drake.node(drake.Path(path_obj).with_extension('hh'))
  + source = drake.node(drake.Path(path_obj).with_extension('moc.cc'))
  qt = builder.toolkit.qt
  res = qt._Qt__moc_cache.get(source)
  if res is None:
  - res = moc_file(qt, builder, source)
  + res = moc_file(qt, builder, header)
  if res is not None:
  qt._Qt__dependencies.setdefault(builder.object, []).append(res)
  logger.log(
  