docker-build: add docker readiness check and update builder image

task/docker-build/0.1/docker-build.yaml

@@ -21,7 +21,7 @@ spec:
     description: Reference of the image docker will produce.
   - name: builder_image
     description: The location of the docker builder image.
-    default: docker.io/library/docker:stable@sha256:18ff92d3d31725b53fa6633d60bed323effb6d5d4588be7b547078d384e0d4bf #tag: stable
+    default: docker.io/library/docker@sha256:2658fda9e8779b94ea1581f4d25214dac9ed144b407902842e5328cce8f861f5 #tag: 29 (linux/amd64)
   - name: dind_image
     description: The location of the docker-in-docker image.
     default: docker:dind
@@ -46,6 +46,41 @@ spec:
   - name: IMAGE_DIGEST
     description: Digest of the image just built.
   steps:
+  - name: docker-info
+    image: $(params.builder_image)
+    env:
+      # Connect to the sidecar over TCP, with TLS.
+      - name: DOCKER_HOST
+        value: tcp://localhost:2376
+      # Verify TLS.
+      - name: DOCKER_TLS_VERIFY
+        value: '1'
+      # Use the certs generated by the sidecar daemon.
+      - name: DOCKER_CERT_PATH
+        value: /certs/client
+      # Retry cap for docker readiness
+      - name: MAX_RETRIES
+        value: "60"
+    workingDir: $(workspaces.source.path)
+    script: |
+      #!/bin/sh
+      set -e
+      i=0
+      max="${MAX_RETRIES:-60}"
+      until docker info >/dev/null 2>&1; do
+        i=$((i+1))
+        if [ "$i" -ge "$max" ]; then
+          echo "ERROR: Docker daemon did not become ready after ${max} attempts."
+          docker info || true
+          exit 1
+        fi
+        echo "Docker not ready yet (attempt ${i}/${max}); sleeping 1s..."
+        sleep 1
+      done
+      echo "Docker daemon is ready."
+    volumeMounts:
+      - mountPath: /certs/client
+        name: dind-certs
   - name: docker-build
     image: $(params.builder_image)
     env: