message: When building file without debug info, include the architecture
  setting in the cflags on Darwin systems.
diff: LEVEL = ../../../make
  OBJCXX_SOURCES := main.mm myobject.mm
  include $(LEVEL)/Makefile.rules
  +CFLAGS_NO_DEBUG =
  +ifeq "$(OS)" "Darwin"
  + CFLAGS_NO_DEBUG += -arch $(ARCH)
  +endif
  # myobject.o needs to be built without debug info
  myobject.o: myobject.mm
  - $(CXX) -c -o $@ $<
  + $(CXX) $(CFLAGS_NO_DEBUG) -c -o $@ $<
  