Fix python 3 syntax error in sym_diff

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@296716 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/libcxx/sym_check/diff.py b/utils/libcxx/sym_check/diff.py
index 55443bd..0821ef6 100644
--- a/utils/libcxx/sym_check/diff.py
+++ b/utils/libcxx/sym_check/diff.py
@@ -43,7 +43,7 @@
             continue
         new_sym = _find_by_key(new, old_sym['name'])
         if (new_sym is not None and not new_sym in old
-                and cmp(old_sym, new_sym) != 0):
+                and old_sym != new_sym):
             changed += [(old_sym, new_sym)]
     return changed