Add runtimeClassName in Kubernetes backend options (#3474)

Resolves #3473

---------

Co-authored-by: Thomas Anderson <127358482+zc-devs@users.noreply.github.com>

pipeline/backend/kubernetes/backend_options.go

@@ -9,6 +9,7 @@ import (
 // BackendOptions defines all the advanced options for the kubernetes backend
 type BackendOptions struct {
 	Resources          Resources         `mapstructure:"resources"`
+	RuntimeClassName   *string           `mapstructure:"runtimeClassName"`
 	ServiceAccountName string            `mapstructure:"serviceAccountName"`
 	NodeSelector       map[string]string `mapstructure:"nodeSelector"`
 	Tolerations        []Toleration      `mapstructure:"tolerations"`

pipeline/backend/kubernetes/pod.go

@@ -117,6 +117,7 @@ func podSpec(step *types.Step, config *config, options BackendOptions) (v1.PodSp
 	var err error
 	spec := v1.PodSpec{
 		RestartPolicy:      v1.RestartPolicyNever,
+		RuntimeClassName:   options.RuntimeClassName,
 		ServiceAccountName: options.ServiceAccountName,
 		ImagePullSecrets:   imagePullSecretsReferences(config.ImagePullSecretNames),
 		HostAliases:        hostAliases(step.ExtraHosts),

pipeline/backend/kubernetes/pod_test.go

@@ -245,6 +245,7 @@ func TestFullPod(t *testing.T) {
 			"nodeSelector": {
 				"storage": "ssd"
 			},
+			"runtimeClassName": "runc",
 			"serviceAccountName": "wp-svc-acc",
 			"securityContext": {
 				"runAsUser": 101,
@@ -289,6 +290,7 @@ func TestFullPod(t *testing.T) {
 		"status": {}
 	}`
 
+	runtimeClass := "runc"
 	hostAliases := []types.HostAlias{
 		{Name: "cloudflare", IP: "1.1.1.1"},
 		{Name: "cf.v6", IP: "2606:4700:4700::64"},
@@ -333,6 +335,7 @@ func TestFullPod(t *testing.T) {
 		SecurityContext:      SecurityContextConfig{RunAsNonRoot: false},
 	}, "wp-01he8bebctabr3kgk0qj36d2me-0", "linux/amd64", BackendOptions{
 		NodeSelector:       map[string]string{"storage": "ssd"},
+		RuntimeClassName:   &runtimeClass,
 		ServiceAccountName: "wp-svc-acc",
 		Tolerations:        []Toleration{{Key: "net-port", Value: "100Mbit", Effect: TaintEffectNoSchedule}},
 		Resources: Resources{