.github/workflows: split the image tag update in two steps

If the images are not created, because they are already available in the
docker image repository, they will have an empty image digest set and
the image tag replacement will wrongly use this empty digest.

Fixes: c5a7787 ("add auto-commit capability to build base images GH workflow")
Signed-off-by: André Martins <andre@cilium.io>

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

@@ -183,10 +183,14 @@ jobs:
           path: image-digest
           retention-days: 1
 
-      - name: Update Runtime and Builder Images
-        if: ${{ steps.cilium-builder-tag-in-repositories.outputs.exists == 'false' || steps.cilium-runtime-tag-in-repositories.outputs.exists == 'false' }}
+      - name: Update Runtime Images
+        if: ${{ steps.cilium-runtime-tag-in-repositories.outputs.exists == 'false' }}
         run: |
           images/runtime/update-cilium-runtime-image.sh "quay.io/${{ env.QUAY_ORGANIZATION_DEV }}/cilium-runtime:${{ steps.runtime-tag.outputs.tag }}@${{ steps.docker_build_release_runtime.outputs.digest }}"
+
+      - name: Update Builder Images
+        if: ${{ steps.cilium-builder-tag-in-repositories.outputs.exists == 'false' }}
+        run: |
           images/builder/update-cilium-builder-image.sh "quay.io/${{ env.QUAY_ORGANIZATION_DEV }}/cilium-builder:${{ steps.builder-tag.outputs.tag }}@${{ steps.docker_build_release_builder.outputs.digest }}"
 
       - name: Commit changes by amending previous commit