message: Only let one signal handler thread crash
  Summary:
  As title. Let other signal handlers sleep a bit and skip unwinding.
  In an effort to better symbolize multi-threaded crashes.
diff: @@ -63,10 +63,18 @@ void crash_backtrace() {
  backtrace_symbols_fd(buf, frames, STDERR_FILENO);
  #endif
  }
  +
  +std::atomic<size_t> g_crashing{0};
  +
  }; // namespace
  void crash_backtrace_handler(int sig) {
  + size_t crashing = g_crashing.fetch_add(1);
  + if (crashing == 0) {
  crash_backtrace();
  + } else {
  + sleep(60); // Sleep a minute, then go on to die if we're still alive.
  + }
  signal(sig, SIG_DFL);
  raise(sig);
  