Use tonistiigi/xx for cross-platform builds

Update the Dockerfile to use tonistiigi/xx to cross-compile the
manager binaries natively and speed up the multi-arch image build
time.

Signed-off-by: Sunny <darkowlzz@protonmail.com>

Dockerfile

@@ -1,6 +1,16 @@
+ARG XX_VERSION=1.0.0-rc.2
+
+FROM --platform=$BUILDPLATFORM tonistiigi/xx:${XX_VERSION} AS xx
+
 # Build the manager binary
-FROM golang:1.16-alpine as builder
+FROM --platform=$BUILDPLATFORM golang:1.16-alpine AS builder
+
+# Copy the build utilities.
+COPY --from=xx / /
+
+ARG TARGETPLATFORM
 
+# Configure workspace.
 WORKDIR /workspace
 
 # copy modules manifests
@@ -20,7 +30,8 @@ COPY controllers/ controllers/
 COPY internal/ internal/
 
 # build without giving the arch, so that it gets it from the machine
-RUN CGO_ENABLED=0 go build -a -o image-reflector-controller main.go
+ENV CGO_ENABLED=0
+RUN xx-go build -a -o image-reflector-controller main.go
 
 FROM alpine:3.13
 

Makefile

@@ -6,6 +6,11 @@ CRD_OPTIONS ?= crd:crdVersions=v1
 ENVTEST_BIN_VERSION?=1.22.0
 KUBEBUILDER_ASSETS?=$(shell $(SETUP_ENVTEST) use -i $(ENVTEST_BIN_VERSION) -p path)
 
+# Allows for defining additional Docker buildx arguments, e.g. '--push'.
+BUILD_ARGS ?=
+# Architectures to build images for.
+BUILD_PLATFORMS ?= linux/amd64,linux/arm64,linux/arm/v7
+
 # Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
 ifeq (,$(shell go env GOBIN))
 GOBIN=$(shell go env GOPATH)/bin
@@ -77,7 +82,10 @@ generate: controller-gen
 
 # Build the docker image
 docker-build: test
-	docker build . -t ${IMG}
+	docker buildx build \
+	--platform=$(BUILD_PLATFORMS) \
+	-t ${IMG} \
+	${BUILD_ARGS} .
 
 # Push the docker image
 docker-push: