message: Add O_NONBLOCK to the serial config for LINUX
  This PR adds a serial config option O_NONBLOCK. This solves the problem of the serial configuration haning when run on a Pocket Beagle.
diff: @@ -74,14 +74,8 @@ ConnectionResult SerialConnection::start()
  ConnectionResult SerialConnection::setup_port()
  {
  -#if defined(LINUX)
  - _fd = open(_serial_node.c_str(), O_RDWR | O_NOCTTY);
  - if (_fd == -1) {
  - LogErr() << "open failed: " << GET_ERROR();
  - return ConnectionResult::CONNECTION_ERROR;
  - }
  -#elif defined(APPLE)
  - // open() hangs on macOS unless you give it O_NONBLOCK
  +#if defined(LINUX) || defined(APPLE)
  + // open() hangs on macOS or Linux devices(e.g. pocket beagle) unless you give it O_NONBLOCK
  _fd = open(_serial_node.c_str(), O_RDWR | O_NOCTTY | O_NONBLOCK);
  if (_fd == -1) {
  LogErr() << "open failed: " << GET_ERROR();
  