[CI] Add kind-in-Docker test to Buildkite CI

.buildkite/example.yml

@@ -5,4 +5,4 @@
     - ls -alp /workdir
     - export PATH=$PATH:/usr/local/go/bin
     - cd /workdir/ray-operator
-    - make test
+    - make test

.buildkite/kind-in-docker.yml

@@ -0,0 +1,18 @@
+- label: kind in Docker
+  instance_size: large
+  image: golang:1.17
+  commands:
+    # Install Go
+    - export PATH=$PATH:/usr/local/go/bin
+
+    # Install kind
+    - curl -Lo ./kind https://kind.sigs.k8s.io/dl/v0.20.0/kind-linux-amd64
+    - chmod +x ./kind
+    - mv ./kind /usr/local/bin/kind
+
+    # Install Docker
+    - bash scripts/install-docker.sh
+
+    # Delete cluster if it already exists
+    - kind delete cluster
+    - kind create cluster

scripts/install-docker.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# Suppress interactive prompts
+export DEBIAN_FRONTEND=noninteractive
+export TZ=America/Los_Angeles
+
+apt-get update -qq && apt-get upgrade -qq
+apt-get install -y -qq curl
+
+curl -o- https://get.docker.com | sh