Fix digest SHA extraction step (#6059)

.github/workflows/release.yml

@@ -47,7 +47,7 @@ jobs:
     # Start a local docker registry to extract the compiled binaries to upload as artifacts and attest them
     services:
       registry:
-        image: registry:3.0.0 # https://hub.docker.com/_/registry/tags
+        image: registry@sha256:1fc7de654f2ac1247f0b67e8a459e273b0993be7d2beda1f3f56fbf1001ed3e7 # v3.0.0
         ports:
           - 5000:5000
     env:
@@ -215,7 +215,7 @@ jobs:
           BAKE_METADATA: ${{ steps.bake_vw.outputs.metadata }}
           BASE_IMAGE: ${{ matrix.base_image }}
         run: |
-          GET_DIGEST_SHA="$(jq -r '.["${BASE_IMAGE}-multi"]."containerimage.digest"' <<< "${BAKE_METADATA}")"
+          GET_DIGEST_SHA="$(jq -r --arg base "$BASE_IMAGE" '.[$base + "-multi"]."containerimage.digest"' <<< "${BAKE_METADATA}")"
           echo "DIGEST_SHA=${GET_DIGEST_SHA}" | tee -a "${GITHUB_ENV}"
 
       # Attest container images