tests/builtin_dir: The most expected thing in sys is exit, test for it.

tests/basics/builtin_dir.py

@@ -5,7 +5,7 @@ print('__name__' in dir())
 
 # dir of module
 import sys
-print('platform' in dir(sys))
+print('exit' in dir(sys))
 
 # dir of type
 print('append' in dir(list))