ci: generate package list during compose via finalize.d

Avoid mounting the built image with buildah (ran out of disk); the
finalize.d hook records the rpm list next to the treefile and release.sh
consumes it directly.

release.sh

@@ -2,7 +2,7 @@
 # Generate a package changelog for a freshly built image and publish it as a
 # Gitea release (instead of committing JSON files under changelogs/).
 #
-# Usage: release.sh <image> <distro> <buildid> <ociarchive>
+# Usage: release.sh <image> <distro> <buildid> <packages-file>
 #
 # The full package list is attached to each release as
 #   packages-<image>-<distro>.txt
@@ -10,21 +10,21 @@
 set -euo pipefail
 
 if [[ $# -lt 4 ]]; then
-  echo "Usage: $0 <image> <distro> <buildid> <ociarchive>" >&2
+  echo "Usage: $0 <image> <distro> <buildid> <packages-file>" >&2
   exit 1
 fi
 
 IMAGE="$1"
 DISTRO="$2"
 BUILDID="$3"
-OCI_ARCHIVE="$4"
+PACKAGES_FILE="$4"
 
 GITEA_URL="${GITEA_URL:-https://git.plabble.org}"
 GITEA_REPO="${GITEA_REPO:-Misthios/bootc-images}"
 TOKEN="${RELEASE_TOKEN:-${GITHUB_TOKEN:-}}"
 
 [[ -n "${TOKEN}" ]] || { echo "RELEASE_TOKEN (or GITHUB_TOKEN) is required" >&2; exit 1; }
-[[ -f "${OCI_ARCHIVE}" ]] || { echo "Missing OCI archive: ${OCI_ARCHIVE}" >&2; exit 1; }
+[[ -f "${PACKAGES_FILE}" ]] || { echo "Missing package list: ${PACKAGES_FILE}" >&2; exit 1; }
 
 API="${GITEA_URL%/}/api/v1/repos/${GITEA_REPO}"
 RELEASE_TAG="${IMAGE}-${DISTRO}.${BUILDID}"
@@ -41,14 +41,9 @@ if curl -fsSL -H "Authorization: token ${TOKEN}" \
   exit 0
 fi
 
-# --- package list from the built image -------------------------------------
-echo "Extracting package list from ${OCI_ARCHIVE} ..."
-export STORAGE_DRIVER=vfs
-ctr="$(buildah from "oci-archive:${OCI_ARCHIVE}")"
-mnt="$(buildah mount "${ctr}")"
-rpm -qa --root "${mnt}" --qf '%{NAME} %{EVR}\n' | sort > "${WORK}/packages-current.txt"
-buildah unmount "${ctr}"
-buildah rm "${ctr}" >/dev/null
+# --- package list from the build -------------------------------------------
+echo "Using package list ${PACKAGES_FILE} ..."
+cp "${PACKAGES_FILE}" "${WORK}/packages-current.txt"
 
 # --- previous package list from the last release ---------------------------
 # Walk the release list (newest first) until we find the newest release for