fix: make install error (pyc being a directory)

Author: Hongbin Huang

Makefile

@@ -5,7 +5,7 @@ help:
 	@fgrep -h "##" $(MAKEFILE_LIST) | fgrep -v fgrep | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
 
 clean: ## Removing cached python compiled files
-	find . -name \*pyc  | xargs  rm -fv
+	find . -name \*pyc  | xargs  rm -rfv
 	find . -name \*pyo | xargs  rm -fv
 	find . -name \*~  | xargs  rm -fv
 	find . -name __pycache__  | xargs  rm -rfv