Use a custom builder image

Use a custom builder image to do all of Ark's builds. This image now
contains k8s.io/code-generator for code generation.

Enable docker in travis to use the builder image.

Signed-off-by: Andy Goldstein <andy.goldstein@gmail.com>

hack/build-image/Dockerfile

@@ -0,0 +1,21 @@
+# Copyright 2018 the Heptio Ark contributors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+FROM gcr.io/heptio-images/golang:1.9-alpine3.6
+
+RUN mkdir -p /go/src/k8s.io && \
+    cd /go/src/k8s.io && \
+    git clone -b kubernetes-1.9.0 https://github.com/kubernetes/code-generator && \
+    git clone -b kubernetes-1.9.0 https://github.com/kubernetes/apimachinery && \
+    echo chmod -R a+w /go

hack/update-generated-crd-code.sh

@@ -1,4 +1,4 @@
-#!/bin/bash -e
+#!/bin/bash
 #
 # Copyright 2017 the Heptio Ark contributors.
 #
@@ -14,13 +14,26 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-HACK_DIR=$(dirname "${BASH_SOURCE}")
-REPO_ROOT=${HACK_DIR}/..
+set -o errexit
+set -o nounset
+set -o pipefail
+set -o xtrace
 
-${REPO_ROOT}/vendor/k8s.io/code-generator/generate-groups.sh \
+if [[ -z "${GOPATH}" ]]; then
+  GOPATH=~/go
+fi
+
+if [[ ! -d "${GOPATH}/src/k8s.io/code-generator" ]]; then
+  echo "k8s.io/code-generator missing from GOPATH"
+  exit 1
+fi
+
+cd ${GOPATH}/src/k8s.io/code-generator
+
+./generate-groups.sh \
   all \
   github.com/heptio/ark/pkg/generated \
   github.com/heptio/ark/pkg/apis \
   ark:v1 \
-  --go-header-file hack/boilerplate.go.txt \
+  --go-header-file ${GOPATH}/src/github.com/heptio/ark/hack/boilerplate.go.txt \
   $@