Build multi-arch images by default

images/fastcgi-helloserver/Makefile

@@ -17,24 +17,33 @@
 # Use the 0.0 tag for testing, it shouldn't clobber any release builds
 TAG ?= 0.0
 
-REGISTRY ?= ingress-controller
-DOCKER ?= docker
+HOSTARCH := $(shell uname -m | sed -e s/x86_64/amd64/ \
+	-e s/s390x/s390x/ \
+	-e s/armv7l/arm/ \
+	-e s/aarch64.*/arm64/)
 
-IMGNAME = fastcgi-helloserver
-IMAGE = $(REGISTRY)/$(IMGNAME)
+ifndef ARCH
+ARCH := $(HOSTARCH)
+endif
+ifeq ($(ARCH),)
+    $(error mandatory variable ARCH is empty)
+endif
+
+REGISTRY ?= ingress-controller
+
+IMAGE = $(REGISTRY)/fastcgi-helloserver
 
 PKG=k8s.io/ingress-nginx/images/fastcgi-helloserver
 
-container: clean build
-	$(DOCKER) buildx build \
+.PHONY: image
+image: build
+	docker buildx build \
 		--load \
-		--platform linux/amd64 \
+		--platform $(ARCH) \
 		-t $(IMAGE):$(TAG) rootfs
 
-build: clean
-	CGO_ENABLED=0 go build -a -installsuffix cgo \
+.PHONY: build
+build:
+	GOARCH=$(ARCH) CGO_ENABLED=0 go build -a -installsuffix cgo \
 		-ldflags "-s -w" \
 		-o rootfs/fastcgi-helloserver ${PKG}/...
-
-clean:
-	$(DOCKER) rmi -f $(IMAGE):$(TAG) || true