message: grpc_util requires ws2_32.lib on windows.
  Add the linkopt to make it work.
diff: load(
  "//tensorflow:tensorflow.bzl",
  + "if_windows",
  "tf_cc_binary",
  "tf_cc_test",
  "tf_cuda_library",
  @@ -39,6 +40,7 @@ cc_library(
  name = "grpc_util",
  srcs = ["grpc_util.cc"],
  hdrs = ["grpc_util.h"],
  + linkopts = if_windows(["-DEFAULTLIB:ws2_32.lib"]),
  deps = [
  "//tensorflow:grpc",
  "//tensorflow:grpc++",
  