Fix platform target to build arm image

Author: jshufro

Makefile

@@ -49,8 +49,8 @@ ${BUILD_DIR}/treegen: ${BIN_DIR}/treegen-${LOCAL_OS}
 
 # docker-builder container
 .PHONY: docker-builder
-docker-builder:
-	VERSION=${VERSION} docker bake -f docker/daemon-bake.hcl builder
+docker-builder: ${BUILD_DIR}/docker-buildx-builder
+	VERSION=${VERSION} docker bake --builder smartnode-builder -f docker/daemon-bake.hcl builder
 
 bin_deps = ${BIN_DIR}
 ifndef NO_DOCKER
@@ -84,6 +84,8 @@ else
 	${local_build_cmd_arm64} -o $@ rocketpool/rocketpool.go
 endif
 
+${BUILD_DIR}:
+	mkdir -p ${BUILD_DIR}
 ${BIN_DIR}:
 	mkdir -p ${BIN_DIR}
 
@@ -107,10 +109,15 @@ else
 	${local_build_cmd_arm64} -o $@ ./treegen/.
 endif
 
+# Multiarch builder
+${BUILD_DIR}/docker-buildx-builder: ${BUILD_DIR}
+	docker buildx create --name smartnode-builder --driver docker-container --platform linux/amd64,linux/arm64
+	touch ${BUILD_DIR}/docker-buildx-builder
+
 # Docker containers
 .PHONY: docker
-docker:
-	VERSION=${VERSION} docker bake -f docker/daemon-bake.hcl smartnode
+docker: ${BUILD_DIR}/docker-buildx-builder
+	VERSION=${VERSION} docker bake --builder smartnode-builder -f docker/daemon-bake.hcl smartnode
 
 .PHONY: docker-push
 docker-push: docker
@@ -135,6 +142,8 @@ docker-latest: docker-push
 docker-prune:
 	docker system prune -af
 	docker buildx prune -af
+	docker buildx rm smartnode-builder
+	rm ${BUILD_DIR}/docker-buildx-builder
 
 .PHONY: lint
 lint:
@@ -149,3 +158,4 @@ test:
 .PHONY: clean
 clean:
 	rm -rf ${BUILD_DIR}
+	docker buildx rm smartnode-builder

docker/daemon-bake.hcl

@@ -14,12 +14,14 @@ target "builder" {
   ]
   target = "smartnode_dependencies"
   platforms = [ "linux/amd64" ]
+  output = [{ "type": "docker" }]
 }
 
 target "smartnode" {
   name = "smartnode-${arch}"
   dockerfile = "docker/rocketpool-dockerfile"
   args = {
+    BUILDPLATFORM = "linux/amd64"
     VERSION = "${VERSION}"
   }
   tags = [
@@ -30,6 +32,6 @@ target "smartnode" {
     arch = [ "amd64", "arm64" ]
   }
   target = "smartnode"
-  platform = "linux/${arch}"
+  platforms = ["linux/${arch}"]
   output = [{ "type": "docker" }]
 }

docker/rocketpool-dockerfile

@@ -1,4 +1,5 @@
-FROM golang:1.21.8-bookworm AS smartnode_dependencies
+FROM --platform=$BUILDPLATFORM golang:1.21.8-bookworm AS smartnode_dependencies
+ARG BUILDPLATFORM
 
 # Install build tools
 RUN dpkg --add-architecture arm64
@@ -21,9 +22,10 @@ RUN --mount=type=cache,target=/gopkgmodcache \
 	GOMODCACHE=/gopkgmodcache go mod download -x && \
 	cp -r /gopkgmodcache /go/pkg/mod
 
-FROM smartnode_dependencies AS build
-ARG TARGETARCH
+FROM --platform=$BUILDPLATFORM smartnode_dependencies AS build
 ARG VERSION
+ARG BUILDPLATFORM
+ARG TARGETARCH
 # Create a directory for the output
 RUN mkdir /build
 # Build the project by mounting ./ to /src, and go buildcache into the image