[CI] Adding CPU docker pipeline (vllm-project#11261)

Signed-off-by: Yuan Zhou <yuan.zhou@intel.com>
Co-authored-by: Kevin H. Luu <kevin@anyscale.com>

.buildkite/release-pipeline.yaml

@@ -55,3 +55,18 @@ steps:
           password-env: DOCKERHUB_TOKEN
     env:
       DOCKER_BUILDKIT: "1"
+
+  - block: "Build CPU release image"
+    key: block-cpu-release-image-build
+    depends_on: ~
+
+  - label: "Build and publish CPU release image"
+    depends_on: block-cpu-release-image-build
+    agents:
+      queue: cpu_queue_postmerge
+    commands:
+      - "aws ecr-public get-login-password --region us-east-1 | docker login --username AWS --password-stdin public.ecr.aws/q9t5s3a7"
+      - "DOCKER_BUILDKIT=1 docker build --build-arg max_jobs=16 --build-arg GIT_REPO_CHECK=1 --tag public.ecr.aws/q9t5s3a7/vllm-cpu-release-repo:$RELEASE_VERSION --progress plain -f Dockerfile.cpu ."
+      - "docker push public.ecr.aws/q9t5s3a7/vllm-cpu-release-repo:$RELEASE_VERSION"
+    env:
+      DOCKER_BUILDKIT: "1"