improve Makefile.

Makefile

@@ -4,18 +4,19 @@ RENDERJS_MIN		= renderjs.min.js
 
 # npm install uglify-js
 UGLIFY_CMD	= $(shell which uglifyjs || echo node ~/node_modules/uglify-js/bin/uglifyjs)
+# npm install jslint
 LINT_CMD	= $(shell which jslint || echo node ~/node_modules/jslint/bin/jslint.js) --terse
 
 auto: build
 build: uglify
 
-uglify:
-	$(UGLIFY_CMD) "$(RENDERJS)" > "$(RENDERJS_MIN)"
+uglify: $(RENDERJS_MIN)
 
-lint:
-	$(LINT_CMD) $(RENDERJS)
+$(RENDERJS_MIN): $(RENDERJS)
+	$(UGLIFY_CMD) "$<" > "$@"
 
-clean:
-	find -name '*~' -delete
-	find -name 'renderjs.min.js' -delete
+lint: $(RENDERJS)
+	$(LINT_CMD) "$<"
 
+clean:
+	rm -f $(RENDERJS_MIN)