-CODE_FOLDERS != find yt_dlp -type f -name '__init__.py' -exec dirname {} \+ | grep -v '/__' | sort
-CODE_FILES != for f in $(CODE_FOLDERS) ; do echo "$$f" | sed 's,$$,/*.py,' ; done
+CODE_FOLDERS_CMD = find yt_dlp -type f -name '__init__.py' | sed 's,/__init__.py,,' | grep -v '/__' | sort
+CODE_FOLDERS != $(CODE_FOLDERS_CMD)
+CODE_FOLDERS ?= $(shell $(CODE_FOLDERS_CMD))
+CODE_FILES_CMD = for f in $(CODE_FOLDERS) ; do echo "$$f" | sed 's,$$,/*.py,' ; done
+CODE_FILES != $(CODE_FILES_CMD)
+CODE_FILES ?= $(shell $(CODE_FILES_CMD))