asio: mark broken on darwin

Started to fail since 1.12.1.

    Undefined symbols for architecture x86_64:
      "boost::chrono::steady_clock::now()", referenced from:
          pinger::start_send() in ping.o
          asio::detail::timer_queue<asio::detail::chrono_time_traits<boost::chrono::steady_clock, asio::wait_traits<boost::chrono::steady_clock> > >::wait_duration_msec(long) const in ping.o
          asio::detail::timer_queue<asio::detail::chrono_time_traits<boost::chrono::steady_clock, asio::wait_traits<boost::chrono::steady_clock> > >::wait_duration_usec(long) const in ping.o
          asio::detail::timer_queue<asio::detail::chrono_time_traits<boost::chrono::steady_clock, asio::wait_traits<boost::chrono::steady_clock> > >::get_ready_timers(asio::detail::op_queue<asio::detail::scheduler_operation>&) in ping.o
          pinger::handle_receive(unsigned long) in p

/cc ZHF #45961