docs: update warning message and formatting in containers.mk

Co-authored-by: aider (ollama_chat/gpt-oss:120b) <aider@aider.chat>

makefiles/containers.mk

@@ -1,35 +1,34 @@
-
 # Get the container (Podman is preferred, but docker can be used too. It may failed with Docker.)
 # TODO: propose nerdctl
-CTN:=$(shell which podman 2>&1 1>/dev/null && echo "podman" || echo "docker")
+CTN := $(shell which podman 2>&1 1>/dev/null && echo "podman" || echo "docker")
 ifeq ($(CTN),podman)
-	CTN_USERMAP=--userns=keep-id
+CTN_USERMAP = --userns=keep-id
 else
-	$(MAKE) warn-docker
-	CTN_USERMAP=--user=$(shell id -u):$(shell id -g) -e HOME=/tmp
+$(warning Warning: Docker is not recommended, use Podman instead.)
+CTN_USERMAP = --user=$(shell id -u):$(shell id -g) -e HOME=/tmp
 endif
 
 # Packaging OCI image, to build rpm, deb, pacman, tar packages
 # We changes the keep-id uid/gid for Podman, so that the user inside the container is the same as the user outside.
 # For Docker, as it doesn't support userns, we use common options, but it may fail...
-PKG_OCI_IMAGE=packaging:fedora
+PKG_OCI_IMAGE = packaging:fedora
 ifeq ($(CTN),podman)
-	# podman
-	PKG_OCI_OPTS:=--rm -it \
+# podman
+PKG_OCI_OPTS := --rm -it \
 	-v ./:/opt/katenary:z \
 	--userns keep-id:uid=1001,gid=1001 \
 	$(PKG_OCI_IMAGE)
 else
-	# docker
-	PKG_OCI_OPTS:=--rm -it \
+# docker
+PKG_OCI_OPTS := --rm -it \
 	-v ./:/opt/katenary:z \
 	-e HOME=/tmp \
 	$(CTN_USERMAP) \
 	$(PKG_OCI_IMAGE)
 endif
-BUILD_IMAGE=docker.io/golang:$(GOVERSION)
+BUILD_IMAGE = docker.io/golang:$(GOVERSION)
 
-GO_OCI:=$(CTN) run --rm -it \
+GO_OCI := $(CTN) run --rm -it \
 	-v $(PWD):/go/src/katenary:z \
 	-w /go/src/katenary \
 	-e CGO_ENABLED=$(CGO_ENABLED) \
@@ -44,6 +43,7 @@ packager-oci-image:
 builder-oci-image:
 	@$(CTN) build -t go-builder:$(GOVERSION) ./oci/builder \
 		--build-arg GOVERSION=$(GOVERSION) 1>/dev/null
+
 katenary-oci:
 	VERSION=$(VERSION) \
 	VERSION=$${VERSION#releases/}; \