stage2 大量优化代码使其自举编译时间大幅缩短

stage2/sys/time.spl

@@ -25,6 +25,10 @@ fn steps(): usize {
     ret vm_timestamp(3);
 }
 
+fn calls(): usize {
+    ret vm_timestamp(5);
+}
+
 fn now_ns(): usize {
     ret vm_timestamp(4);
 }