builtin/k8s/task: Explicitly set container env var for Kaniko

.changelog/3322.txt

@@ -0,0 +1,5 @@
+```release-note:bug
+plugin/k8s: Ensure `container=docker` environment variable is set for Kaniko
+to properly detect running inside a container, which prevented on-demand
+runners from working on Kubernetes 1.23.
+```

builtin/k8s/task.go

@@ -270,6 +270,15 @@ func (p *TaskLauncher) StartTask(
  })
  }
 
+ // NOTE(briancain): This is here to help kaniko detect that this is a docker container.
+ // See https://github.com/GoogleContainerTools/kaniko/blob/7e3954ac734534ce5ce68ad6300a2d3143d82f40/vendor/github.com/genuinetools/bpfd/proc/proc.go#L138
+ // for more info.
+ log.Warn("temporarily setting 'container=docker' environment variable to patch Kaniko working on Kubernetes 1.23")
+ env = append(env, corev1.EnvVar{
+ Name: "container",
+ Value: "docker",
+ })
+
  // If the user is using the latest tag, then don't specify an overriding pull policy.
  // This by default means kubernetes will always pull so that latest is used.
  pullPolicy := corev1.PullIfNotPresent