Refactor build scripts to consistently use Podman for image building

rocky9/build.sh

@@ -5,16 +5,10 @@ set -eu
 IMAGE_NAME="${IMAGE_NAME:-rocky9-source-stack}"
 SCRIPT_DIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
 
-if [ -n "${CONTAINER_ENGINE:-}" ]; then
-    ENGINE=$CONTAINER_ENGINE
-elif command -v docker >/dev/null 2>&1; then
-    ENGINE=docker
-elif command -v podman >/dev/null 2>&1; then
-    ENGINE=podman
-else
-    echo "Error: Docker or Podman is required." >&2
+if ! command -v podman >/dev/null 2>&1; then
+    echo "Error: Podman is required." >&2
     exit 1
 fi
 
-echo "Building image $IMAGE_NAME with $ENGINE ..."
-exec "$ENGINE" build --tag "$IMAGE_NAME" "$SCRIPT_DIR"
+echo "Building image $IMAGE_NAME with podman ..."
+exec podman build --tag "$IMAGE_NAME" "$SCRIPT_DIR"