fix(ci/github/agent-container): will --push make the right metadata file?

Author: ayuskauskas

.github/workflows/agent-container.yaml

@@ -81,6 +81,7 @@ jobs:
           esac
           export TAGS=$TAGS
           export REGISTRY=${REGISTRY@L}
+          export BUILD_ARGS="--push"
           make docker-build-only agent_version=${AGENT_VERSION}
           cat metadata.json
           echo "digest=$(cat metadata.json | jq -r .\"containerimage.digest\")" >> $GITHUB_OUTPUT