Fix d8 build error on a fresh checkout.

tools/js2c.py

 #!/usr/bin/env python
 #
 # Copyright 2006-2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 257 matching lines @@
 
 GET_DEBUGGER_SCRIPT_NAME_CASE = """\
     if (index == %(i)i) return Vector<const char>("%(name)s", %(length)i);
 """
 
 def JS2C(source, target, env):
   ids = []
   debugger_ids = []
   modules = []
   # Locate the macros file name.
-  consts = {}
-  macros = {}
+  consts = []
+  macros = []
   for s in source:
     if 'macros.py' == (os.path.split(str(s))[1]):
       (consts, macros) = ReadMacros(ReadLines(str(s)))
     else:
       modules.append(s)
 
   # Build source code lines
   source_lines = [ ]
 
   minifier = jsmin.JavaScriptMinifier()
@@ skipping 81 matching lines @@
 
 def main():
   natives = sys.argv[1]
   natives_empty = sys.argv[2]
   type = sys.argv[3]
   source_files = sys.argv[4:]
   JS2C(source_files, [natives, natives_empty], { 'TYPE': type })
 
 if __name__ == "__main__":
   main()