use of system in parameters in synch

src/kernel/thread_manager.rs

@@ -94,6 +94,7 @@ impl ThreadManager {
 
             let mut next_thread = self.g_scheduler.find_next_to_run();
             while next_thread.is_none() {
+                eprintln!("Nobody to run => idle");
                 machine.interrupt.idle();
                 next_thread = self.g_scheduler.find_next_to_run();
             }