Minimal changes to make the "freeze" tool work again.
There are other issues left, but these were basics (e.g. keys().sort()).
diff --git a/Tools/freeze/makemakefile.py b/Tools/freeze/makemakefile.py
index ff8b15a..32e804c 100644
--- a/Tools/freeze/makemakefile.py
+++ b/Tools/freeze/makemakefile.py
@@ -5,8 +5,7 @@
 def makemakefile(outfp, makevars, files, target):
     outfp.write("# Makefile generated by freeze.py script\n\n")
 
-    keys = makevars.keys()
-    keys.sort()
+    keys = sorted(makevars.keys())
     for key in keys:
         outfp.write("%s=%s\n" % (key, makevars[key]))
     outfp.write("\nall: %s\n\n" % target)