message: Avoid logspam if ptxas is not found.
  Log the "not found" message only once.
diff: @@ -310,8 +310,12 @@ port::StatusOr<RedzoneCheckStatus> RedzoneAllocator::CheckRedzones(
  if (compiled_ptx_or.ok()) {
  compiled_ptx = compiled_ptx_or.ValueOrDie();
  } else {
  + static std::once_flag ptxas_not_found_logged;
  + std::call_once(ptxas_not_found_logged, [&]() {
  LOG(WARNING) << compiled_ptx_or.status().ToString()
  - << "\nRelying on driver to perform ptx compilation";
  + << "\nRelying on driver to perform ptx compilation. "
  + << "This message will be only logged once.";
  + });
  }
  ScopedDeviceMemory<uint64> out_param =
  