Added GitHub Actions workflow for building base images

Manually triggered workflow that builds and pushes container images to
ghcr.io. Builds all platforms in parallel via a matrix strategy.

Ticket: ENT-13784
Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>

Author: larsewi

.github/workflows/build-base-images.yml

@@ -0,0 +1,31 @@
+name: Build base images
+
+on:
+  workflow_dispatch:
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    strategy:
+      matrix:
+        platform:
+          - ubuntu-20
+          - ubuntu-22
+          - ubuntu-24
+          - debian-11
+          - debian-12
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+
+      - name: Log in to ghcr.io
+        uses: docker/login-action@v4
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push image
+        run: ./build-in-container.py --platform ${{ matrix.platform }} --push-image

build-in-container.py

@@ -152,9 +152,25 @@ def pull_image(platform_name):
     return ref
 
 
+def image_exists_in_registry(platform_name):
+    """Check if an image tag already exists in the registry."""
+    ref = registry_image_ref(platform_name)
+    result = subprocess.run(
+        ["docker", "manifest", "inspect", ref],
+        capture_output=True,
+        text=True,
+    )
+    return result.returncode == 0
+
+
 def push_image(platform_name, local_tag):
     """Tag a local image with the registry reference and push it."""
     ref = registry_image_ref(platform_name)
+
+    if image_exists_in_registry(platform_name):
+        log.error(f"Image {ref} already exists. Bump IMAGE_VERSION.")
+        sys.exit(1)
+
     log.info(f"Tagging {local_tag} as {ref}...")
     result = subprocess.run(["docker", "tag", local_tag, ref])
     if result.returncode != 0: