message: Fix build breakage with downloadable clang and -fopenmp.
  By disabling openmp when building with clang.
  If we want to enable openmp with clang, we'll probably have to have libomp as
  an explicit dependency.
  This fixes a breakage found by OS CI:
diff: exports_files(["LICENSE"])
  +config_setting(
  + name = "clang_linux_x86_64",
  + values = {
  + "cpu": "k8",
  + "define": "using_cuda_clang=true",
  + },
  +)
  +
  cc_library(
  name = "mkl_dnn",
  srcs = glob([
  @@ -9,8 +17,11 @@ cc_library(
  hdrs = glob(["include/*"]),
  copts = ["-fexceptions"] + select({
  "@org_tensorflow//tensorflow:linux_x86_64": [
  - "-fopenmp",
  + "-fopenmp", # only works with gcc
  ],
  + # TODO(ibiryukov): enable openmp with clang by including libomp as a
  + # dependency.
  + ":clang_linux_x86_64": [],
  "//conditions:default": [],
  }),
  includes = [
  