redo-ifchange: remove special case for zero arguments.

Not sure why I put there, but special cases aren't worth the hassle.

builder.py

@@ -297,6 +297,7 @@ def main(targets, shouldbuildfunc):
     # In the first cycle, we just build as much as we can without worrying
     # about any lock contention.  If someone else has it locked, we move on.
     seen = {}
+    lock = None
     for t in targets:
         if t in seen:
             continue

redo-ifchange.py

@@ -1,7 +1,5 @@
 #!/usr/bin/python
 import sys, os
-if not sys.argv[1:]:
-    sys.exit(0)  # nothing to do, so we can't possibly do it wrong
 
 import vars_init
 vars_init.init(sys.argv[1:])