ci: bake cached toolchain into Podman agent and fix nested Buildah [CI]

ci/publish-manifest.sh

@@ -13,6 +13,11 @@ dir="${3:?manifest dir}"
 [[ -s "$dir/manifest.json" && -s "$dir/manifest.sig" ]] || { echo "$dir needs manifest.json and manifest.sig" >&2; exit 2; }
 
 ref="${repository}-manifest:${channel}"
+if [[ -z "${CONTAINERS_STORAGE_CONF:-}" ]]; then
+  root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+  source "$root/ci/buildah-env.sh"
+  moshiro_setup_buildah "${BUILDAH_HOME:-/home/justme/woodpecker/buildah-home/manifest-${repository##*/}-$channel}"
+fi
 local_name="localhost/moshiro-manifest-build:$$"
 container="$(buildah from scratch)"
 trap 'buildah rm "$container" >/dev/null 2>&1 || true; buildah rmi "$local_name" >/dev/null 2>&1 || true' EXIT