message: Update XLA for tool_output_file->ToolOutputFile (LLVM r314050).
  This will require an LLVM version bump for workspace.bzl.
diff: @@ -245,7 +245,7 @@ void AddOptimizationPasses(unsigned opt_level, unsigned size_level,
  // Emits the given module to a bit code file.
  void EmitBitcodeToFile(const Module& module, tensorflow::StringPiece filename) {
  std::error_code error_code;
  - llvm::tool_output_file outfile(filename.ToString().c_str(), error_code,
  + llvm::ToolOutputFile outfile(filename.ToString().c_str(), error_code,
  llvm::sys::fs::F_None);
  if (error_code) {
  LOG(FATAL) << "opening bitcode file for writing: " << error_code.message();
  