Add support for variable subsitution in Ingress hosts

pkg/commands/build/testdata/testcase-variable-ref-ingress/expected.yaml

@@ -0,0 +1,53 @@
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app.kubernetes.io/component: nginx
+  name: kustomized-nginx
+spec:
+  ports:
+  - name: http
+    port: 80
+    protocol: TCP
+    targetPort: http
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app.kubernetes.io/component: nginx
+  name: kustomized-nginx
+spec:
+  selector:
+    matchLabels:
+      app.kubernetes.io/component: nginx
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/component: nginx
+    spec:
+      containers:
+      - image: nginx:1.15.7-alpine
+        name: nginx
+        ports:
+        - containerPort: 80
+          name: http
+---
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  labels:
+    app.kubernetes.io/component: nginx
+  name: kustomized-nginx
+spec:
+  rules:
+  - host: kustomized-nginx.example.com
+    http:
+      paths:
+      - backend:
+          serviceName: kustomized-nginx
+          servicePort: 80
+        path: /
+  tls:
+  - hosts:
+    - kustomized-nginx.example.com