Example building a docker image with Kaniko (jenkinsci#312)

The docker-registry secret type crates a .dockercfg file that needs to be put in root

It does not create the new .docker/config.json format

examples/kaniko.groovy

@@ -0,0 +1,43 @@
+/**
+ * This pipeline will build and deploy a Docker image with Kaniko
+ * https://github.com/GoogleContainerTools/kaniko
+ * without needing a Docker host
+ *
+ * You need to create a jenkins-docker-cfg secret with your docker config
+ * as described in
+ * https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/#create-a-secret-in-the-cluster-that-holds-your-authorization-token
+ */
+
+ def label = "kaniko-${UUID.randomUUID().toString()}"
+
+ podTemplate(name: 'kaniko', label: label, yaml: """
+ kind: Pod
+ metadata:
+   name: kaniko
+ spec:
+   containers:
+   - name: kaniko
+     image: csanchez/kaniko:jenkins # we need a patched version of kaniko for now
+     imagePullPolicy: Always
+     command:
+     - cat
+     tty: true
+     volumeMounts:
+       - name: jenkins-docker-cfg
+         mountPath: /root
+   volumes:
+     - name: jenkins-docker-cfg
+       secret:
+         secretName: regcred
+ """
+   ) {
+
+   node(label) {
+     stage('Build with Kaniko') {
+       git 'https://github.com/jenkinsci/docker-jnlp-slave.git'
+       container('kaniko') {
+           sh '/kaniko/executor -c . --insecure-skip-tls-verify --destination=mydockerregistry:5000/myorg/myimage'
+       }
+     }
+   }
+ }