NO_CLEAN: No need to run delete-old if the directories don't exist.

X-MFC-With:	r321443
MFC after:	1 month
Sponsored by:	Dell EMC Isilon

Makefile.inc1

@@ -760,10 +760,12 @@ _worldtmp: .PHONY
 	rm -rf ${LIBCOMPATTMP}
 .endif
 .else
+.if exists(${WORLDTMP})
 	@echo ">>> Deleting stale files in build tree..."
 	${_+_}cd ${.CURDIR}; ${WMAKE} -DBATCH_DELETE_OLD_FILES \
 	    delete-old delete-old-libs >/dev/null
-.if defined(LIBCOMPAT)
+.endif
+.if defined(LIBCOMPAT) && exists(${LIBCOMPATTMP})
 	${_+_}cd ${.CURDIR}; ${WMAKE} -DBATCH_DELETE_OLD_FILES \
 	    DESTDIR=${LIBCOMPATTMP} \
 	    delete-old delete-old-libs >/dev/null