makefile: add missing dependency for merged.lib

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -337,7 +337,7 @@ $(DONT_USE_LIBS): $$(filter %$$(@F) %$$(@F).gz,$(LIB_FILES))
 	@mkdir -p $(OBJECTS_DIR)/lib
 	$(UTILS_DIR)/preprocessLib.py -i $^ -o $@
 
-$(OBJECTS_DIR)/lib/merged.lib:
+$(OBJECTS_DIR)/lib/merged.lib: $(DONT_USE_LIBS)
 	$(UTILS_DIR)/mergeLib.pl $(PLATFORM)_merged $(DONT_USE_LIBS) > $@
 
 # Pre-process KLayout tech