Cleanup/refactor build scripts for DOM codegen

Prior to this commit, the script codegen makefile relied on an
intermediary pythonpath.py file that handled python dependencies and
incorporated a couple hacks to get the codegen building working. This
commit removes that intermediary file and attempts to make the script
codegen build process cleaner.

components/script/dom/bindings/codegen/pythonpath.py

@@ -1,61 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-"""
-Run a python script, adding extra directories to the python path.
-"""
-
-
-def main(args):
-    def usage():
-        print >>sys.stderr, "pythonpath.py -I directory script.py [args...]"
-        sys.exit(150)
-
-    paths = []
-
-    while True:
-        try:
-            arg = args[0]
-        except IndexError:
-            usage()
-
-        if arg == '-I':
-            args.pop(0)
-            try:
-                path = args.pop(0)
-            except IndexError:
-                usage()
-
-            paths.append(os.path.abspath(path))
-            continue
-
-        if arg.startswith('-I'):
-            paths.append(os.path.abspath(args.pop(0)[2:]))
-            continue
-
-        if arg.startswith('-D'):
-            os.chdir(args.pop(0)[2:])
-            continue
-
-        break
-
-    script = args[0]
-
-    sys.path[0:0] = [os.path.abspath(os.path.dirname(script))] + paths
-    sys.argv = args
-    sys.argc = len(args)
-
-    frozenglobals['__name__'] = '__main__'
-    frozenglobals['__file__'] = script
-
-    execfile(script, frozenglobals)
-
-# Freeze scope here ... why this makes things work I have no idea ...
-frozenglobals = globals()
-
-import sys
-import os
-
-if __name__ == '__main__':
-    main(sys.argv[1:])