chore: fix sourcing of venv activate

Author: git-developer

Dockerfile

@@ -70,7 +70,7 @@ RUN <<EOR
 
 	python -m build --wheel
 	python -m venv .env
-	.env/bin/activate
+	. .env/bin/activate
 	pip install --prefix "${TARGET}/usr" dist/*.whl
 	# fix shebangs of scripts from '#!/work/.env/bin/python'
 	find "${TARGET}/usr/bin" -type f | xargs sed -i 's:work/.env:usr:'