recipes: add multi-layer OCI example recipes

Add example recipes demonstrating multi-layer OCI image building:

alpine-oci-base_3.19.bb:
  - Fetches Alpine 3.19 from Docker Hub using container-bundle
  - Uses CONTAINER_BUNDLE_DEPLOY for use as OCI_BASE_IMAGE source
  - Pinned digest for reproducible builds

app-container-alpine.bb:
  - Demonstrates external base image usage
  - Layers Yocto packages (busybox) on top of Alpine
  - Uses OCI_IMAGE_CMD for Docker-like behavior

app-container-layered.bb:
  - Demonstrates local base image usage
  - Layers Yocto packages on top of container-base
  - Uses OCI_IMAGE_CMD for Docker-like behavior

Both app containers produce 2-layer OCI images where the base layer
is shared, reducing storage and transfer costs.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/recipes-containers/oci-base-images/alpine-oci-base_3.19.bb b/recipes-containers/oci-base-images/alpine-oci-base_3.19.bb
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+++ b/recipes-containers/oci-base-images/alpine-oci-base_3.19.bb
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: MIT
+#
+# Alpine OCI base image for use with OCI_BASE_IMAGE
+#
+# This recipe fetches Alpine Linux from Docker Hub and deploys it to
+# DEPLOY_DIR_IMAGE for use as a base layer in multi-layer OCI builds.
+#
+# Usage in your container recipe:
+#   OCI_BASE_IMAGE = "alpine-oci-base"
+#   IMAGE_INSTALL = "base-files busybox myapp"
+#
+# The Alpine layers will be preserved, and your IMAGE_INSTALL packages
+# are added as an additional layer on top.
+
+SUMMARY = "Alpine Linux OCI base image"
+DESCRIPTION = "Fetches Alpine Linux from Docker Hub for use as an OCI base layer"
+HOMEPAGE = "https://alpinelinux.org/"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
+
+inherit container-bundle
+
+# Remote container from Docker Hub
+CONTAINER_BUNDLES = "docker.io/library/alpine:3.19"
+
+# REQUIRED: Pinned digest for reproducible builds
+# Get with: skopeo inspect docker://docker.io/library/alpine:3.19 | jq -r '.Digest'
+CONTAINER_DIGESTS[docker.io_library_alpine_3.19] = "sha256:6baf43584bcb78f2e5847d1de515f23499913ac9f12bdf834811a3145eb11ca1"
+
+# Enable deployment to DEPLOY_DIR_IMAGE for use as OCI base layer
+CONTAINER_BUNDLE_DEPLOY = "1"