fix typo

makefile

@@ -149,7 +149,7 @@ image:
 
 #:::::::::::::::::::::::::::::: pbuilder management :::::::::::::::::::::::
 .PHONY: pbuilder_create
-pbuilder-create:
+pbuilder_create:
 	$(MAKE) $(PBUILDER_CHROOT)
 
 $(PBUILDER_CHROOT): $(PBUILDER_RC)
@@ -157,5 +157,5 @@ $(PBUILDER_CHROOT): $(PBUILDER_RC)
 
 #TODO: should only update if not updated for a day
 .PHONY: pbuilder_update
-pbuilder-update:
+pbuilder_update:
 	pbuilder update --basetgz $(PBUILDER_CHROOT) --configfile $(PBUILDER_RC)