Multi-platform docker image support

Dockerfile

@@ -1,6 +1,8 @@
 # -----------------------------------------------------------------------------
 # Build...
 FROM golang:1.21-alpine3.19 AS build
+ARG TARGETOS
+ARG TARGETARCH
 
 WORKDIR /popeye
 
@@ -9,11 +11,12 @@ COPY internal internal
 COPY cmd cmd
 COPY types types
 COPY pkg pkg
-RUN apk --no-cache add make git gcc libc-dev curl ca-certificates binutils-gold && make build
+RUN apk --no-cache add make git gcc libc-dev curl ca-certificates binutils-gold && \
+    CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} make build
 
 # -----------------------------------------------------------------------------
 # Image...
-FROM alpine:3.19.0
+FROM alpine:3.19.1
 
 COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 COPY --from=build /popeye/execs/popeye /bin/popeye

Makefile

@@ -4,7 +4,8 @@ VERSION  := v0.11.3
 GIT      := $(shell git rev-parse --short HEAD)
 DATE     := $(shell date +%FT%T%Z)
 IMG_NAME := derailed/popeye
-IMAGE    := ${IMG_NAME}:${VERSION}
+IMAGE    ?= ${IMG_NAME}:${VERSION}
+PLATFORMS ?= linux/arm64,linux/amd64,linux/s390x,linux/ppc64le
 
 default: help
 
@@ -26,5 +27,14 @@ img:  ## Build Docker Image
 push: img ## Push Docker Image
 	@docker push ${IMAGE}
 
+buildx: ## Build and push docker image for cross-platform support
+	# copy existing Dockerfile and insert --platform=${BUILDPLATFORM} into Dockerfile.cross, and preserve the original Dockerfile
+	sed -e '1 s/\(^FROM\)/FROM --platform=\$$\{BUILDPLATFORM\}/; t' -e ' 1,// s//FROM --platform=\$$\{BUILDPLATFORM\}/' Dockerfile > Dockerfile.cross
+	- docker buildx create --name popeye-builder
+	docker buildx use popeye-builder
+	- docker buildx build --push --platform=$(PLATFORMS) --tag ${IMAGE} -f Dockerfile.cross .
+	- docker buildx rm popeye-builder
+	rm Dockerfile.cross
+
 help:
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[38;5;69m%-30s\033[38;5;38m %s\033[0m\n", $$1, $$2}'