ensure new py gets copied

Makefile

@@ -20,12 +20,16 @@ endif
 
 
 # you should have xcb-proto installed to run this
-xcffib: module/*.py xcffib.cabal $(shell find . -path ./test -prune -false -o -name \*.hs)
+xcffib: xcffib_py_files xcffib.cabal $(shell find . -path ./test -prune -false -o -name \*.hs)
 	$(GEN) --input $(XCBDIR) --output ./xcffib
-	cp ./module/*py ./xcffib/
 	touch ./xcffib/py.typed
 	sed -i -e "s/__xcb_proto_version__ = .*/__xcb_proto_version__ = \"${XCBVER}\"/" xcffib/__init__.py
 
+xcffib_py_files: $(addprefix xcffib/, $(notdir $(wildcard module/*.py)))
+
+xcffib/%.py: module/%.py
+	cp $^ $@
+
 .PHONY: xcffib-fmt
 xcffib-fmt: module/*.py
 ifeq (${PARALLEL},)