--- Ice-3.5.0.original/cpp/config/Make.rules.Darwin	2013-03-11 15:19:46.000000000 +0000
+++ Ice-3.5.0/cpp/config/Make.rules.Darwin	2013-07-23 13:49:31.000000000 +0100
@@ -11,9 +11,9 @@
 # This file is included by Make.rules when uname is Darwin.
 #
 
-CXX			= xcrun clang++
+CXX			?= xcrun clang++
 
-CXXFLAGS		= -Wall -Werror -D_REENTRANT
+CXXFLAGS		?= -Wall -Werror -D_REENTRANT
 
 ifeq ($(OPTIMIZE),yes)
      #