vendors/execa.js/listener
        sigListeners[sig] = function listener() {
          if (!processOk(global.process)) {
            return;
          }
          var listeners = process4.listeners(sig);
          if (listeners.length === emitter.count) {
            unload();
            emit("exit", null, sig);
            emit("afterexit", null, sig);
            if (isWin && sig === "SIGHUP") {
              sig = "SIGINT";
            }
            process4.kill(process4.pid, sig);
          }
        };