From de97998a54de47b15c7d4feb17784cf4e9124a06 Mon Sep 17 00:00:00 2001
From: Nicolas Duchon <nicolas.duchon@gmail.com>
Date: Thu, 21 Dec 2023 02:41:46 +0100
Subject: [PATCH] build: switch to go cross compilation

---
 Dockerfile.alpine | 21 ++++++++++++++++-----
 Dockerfile.debian | 22 ++++++++++++++++------
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/Dockerfile.alpine b/Dockerfile.alpine
index 1f9abfc2..e4be96bb 100644
--- a/Dockerfile.alpine
+++ b/Dockerfile.alpine
@@ -1,9 +1,13 @@
 ARG DOCKER_GEN_VERSION=main
 
 # Build docker-gen from scratch
-FROM golang:1.20.12-alpine as go-builder
+FROM --platform=$BUILDPLATFORM golang:1.20.12-alpine as go-builder
+
+ENV CGO_ENABLED=0
+
+ARG DOCKER_GEN_VERSION TARGETOS TARGETARCH TARGETVARIANT
+ENV GOOS=$TARGETOS GOARCH=$TARGETARCH VARIANT=$TARGETVARIANT
 
-ARG DOCKER_GEN_VERSION
 WORKDIR /build
 
 # Install the dependencies
@@ -11,9 +15,16 @@ COPY . .
 RUN go mod download
 
 # Build the docker-gen executable
-RUN GOOS=linux CGO_ENABLED=0 go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" -o docker-gen ./cmd/docker-gen
-
-FROM alpine:3.19.0
+RUN set -eux; \
+	case "$GOARCH" in \
+		arm) export GOARM="${VARIANT#v}" ;; \
+		amd64) export GOAMD64="$VARIANT" ;; \
+		*) [ -z "$VARIANT" ] ;; \
+	esac; \
+	go env | grep -E 'OS=|ARCH=|ARM=|AMD64='; \
+    go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" -o docker-gen ./cmd/docker-gen
+
+FROM --platform=$TARGETPLATFORM alpine:3.19.0
 
 ARG DOCKER_GEN_VERSION
 ENV DOCKER_GEN_VERSION=${DOCKER_GEN_VERSION} \
diff --git a/Dockerfile.debian b/Dockerfile.debian
index 5864af61..eacddd7e 100644
--- a/Dockerfile.debian
+++ b/Dockerfile.debian
@@ -1,9 +1,12 @@
 ARG DOCKER_GEN_VERSION=main
 
 # Build docker-gen from scratch
-FROM golang:1.20.12 as go-builder
+FROM --platform=$BUILDPLATFORM golang:1.20.12 as go-builder
 
-ARG DOCKER_GEN_VERSION
+ENV CGO_ENABLED=0
+
+ARG DOCKER_GEN_VERSION TARGETOS TARGETARCH TARGETVARIANT
+ENV GOOS=$TARGETOS GOARCH=$TARGETARCH VARIANT=$TARGETVARIANT
 
 WORKDIR /build
 
@@ -12,12 +15,19 @@ COPY . .
 RUN go mod download
 
 # Build the docker-gen executable
-RUN GOOS=linux CGO_ENABLED=0 go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" -o docker-gen ./cmd/docker-gen
+RUN set -eux; \
+	case "$GOARCH" in \
+		arm) export GOARM="${VARIANT#v}" ;; \
+		amd64) export GOAMD64="$VARIANT" ;; \
+		*) [ -z "$VARIANT" ] ;; \
+	esac; \
+	go env | grep -E 'OS=|ARCH=|ARM=|AMD64='; \
+    go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" -o docker-gen ./cmd/docker-gen
 
-FROM debian:12.4-slim
+FROM --platform=$TARGETPLATFORM debian:12.4-slim
 
-ARG VERSION
-ENV DOCKER_GEN_VERSION=${VERSION} \
+ARG DOCKER_GEN_VERSION
+ENV DOCKER_GEN_VERSION=${DOCKER_GEN_VERSION} \
     DOCKER_HOST=unix:///tmp/docker.sock
 
 # Install packages required by the image