Migrate the webhook-certgen program to inside ingress repo (#7475)

images/kube-webhook-certgen/rootfs/Dockerfile

@@ -0,0 +1,29 @@
+# Copyright 2021 The Kubernetes Authors. All rights reserved.
+#
+# 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 --platform=$BUILDPLATFORM golang:1.16 as builder
+ARG BUILDPLATFORM
+ARG TARGETARCH
+
+WORKDIR /workspace
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=${TARGETARCH} go build -a -o kube-webhook-certgen main.go
+
+FROM --platform=$BUILDPLATFORM gcr.io/distroless/static:nonroot
+ARG BUILDPLATFORM
+ARG TARGETARCH
+WORKDIR /
+COPY --from=builder /workspace/kube-webhook-certgen /kube-webhook-certgen
+USER 65532:65532
+ENTRYPOINT ["/kube-webhook-certgen"]