docs: announce venv creation before installing packages (python#117036)

Doc/Makefile

@@ -163,6 +163,7 @@ venv:
 		echo "venv already exists."; \
 		echo "To recreate it, remove it first with \`make clean-venv'."; \
 	else \
+		echo "Creating venv in $(VENVDIR)"; \
 		$(PYTHON) -m venv $(VENVDIR); \
 		$(VENVDIR)/bin/python3 -m pip install --upgrade pip; \
 		$(VENVDIR)/bin/python3 -m pip install -r $(REQUIREMENTS); \