Add Docker image support multi OS archs

Dockerfile

@@ -12,13 +12,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.18 AS build-env
+ARG BUILDPLATFORM=linux/amd64
+FROM --platform=$BUILDPLATFORM golang:1.18 AS build-env
 RUN mkdir -p /go/src/sig.k8s.io/gateway-api
 WORKDIR /go/src/sig.k8s.io/gateway-api
 COPY  . .
+ARG TARGETARCH
 ARG TAG
 ARG COMMIT
-RUN CGO_ENABLED=0 GOARCH=amd64 GOOS=linux go build -a -o gateway-api-webhook \
+RUN CGO_ENABLED=0 GOARCH=$TARGETARCH GOOS=linux go build -a -o gateway-api-webhook \
       -ldflags "-s -w -X main.VERSION=$TAG -X main.COMMIT=$COMMIT" ./cmd/admission
 
 FROM gcr.io/distroless/static:nonroot

README.md

@@ -67,4 +67,3 @@ Participation in the Kubernetes community is governed by the
 [spec]: https://gateway-api.sigs.k8s.io/v1alpha2/references/spec
 [concepts]: https://gateway-api.sigs.k8s.io/concepts/api-overview
 [security-model]: https://gateway-api.sigs.k8s.io/concepts/security-model
-

hack/build-and-push.sh

@@ -64,10 +64,9 @@ fi
 
 # First, build the image, with the version info passed in.
 # Note that an image will *always* be built tagged with the GIT_TAG, so we know when it was built.
-docker build --build-arg COMMIT=${COMMIT} --build-arg TAG=${BINARY_TAG} \
-  			-t ${REGISTRY}/admission-server:${GIT_TAG} .
-docker push ${REGISTRY}/admission-server:${GIT_TAG}
+docker buildx build --build-arg COMMIT=${COMMIT} --build-arg TAG=${BINARY_TAG} \
+  			-t ${REGISTRY}/admission-server:${GIT_TAG} . --platform linux/amd64,linux/arm64 --push
 
 # Then, we add an extra version tag - either :latest or semver.
-docker tag ${REGISTRY}/admission-server:${GIT_TAG} ${REGISTRY}/admission-server:${VERSION_TAG}
-docker push ${REGISTRY}/admission-server:${VERSION_TAG}
+docker buildx build --build-arg COMMIT=${COMMIT} --build-arg TAG=${BINARY_TAG} \
+  			-t ${REGISTRY}/admission-server:${VERSION_TAG} . --platform linux/amd64,linux/arm64 --push