Store difference between Ableton Link clock and POSIX system clock

gistfile1.txt

    static long diff = 0;

    const auto time = state.link.clock().micros();
    unsigned long milliseconds_since_epoch = 
      std::chrono::duration_cast<std::chrono::milliseconds>
      (std::chrono::system_clock::now().time_since_epoch()).count();
    
    if (diff == 0) {
      // POSIX is millis and Link is micros.. Not sure if that `+500` helps
      diff = ((milliseconds_since_epoch*1000 + 500) - std::chrono::microseconds(time).count());
    }