The hook_cron_pre_execute($function, &$hook) is invoked just before running the cron function.

### Example

Call another function instead of the defined

    function hook_cron_pre_execute($function, &$hook) {
      if ($function == 'node_cron') {
        $hook['callback'] = 'mymodule_steal_cron_function_from_node_module';
      }
    }

    function mymodule_steal_cron_function_from_node_module() {
      error_log('PWNED');
    }