avoid rebuilding dependent files if the generated busy.h and ringtone.h

do not change.

Ths masks (but does not solve) a but that i am seeing in doing a
'gmake install' without donig a 'gmake all' first.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@94713 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/Makefile

@@ -89,10 +89,16 @@ gentone: gentone.c
 	$(CMD_PREFIX) $(HOST_CC) -o $@ $^ -lm
 
 busy.h: gentone
+	-@mv $@ $@.tmp
 	./gentone busy 480 620
+	@cmp -s $@.tmp $@ && mv $@.tmp $@
+	-@rm -f  $@.tmp
 
 ringtone.h: gentone
+	-@mv $@ $@.tmp
 	./gentone ringtone 440 480
+	@cmp -s $@.tmp $@ && mv $@.tmp $@
+	-@rm -f  $@.tmp
 
 $(if $(filter chan_iax2,$(EMBEDDED_MODS)),modules.link,chan_iax2.so): iax2-parser.o iax2-provision.o