Use single-arch in dockerfile

This is necessary since the builder no longer passes the platform flag
to the build. This would lead to dockerfiles that are mixing multi and single
arch stages to pull the wrong architecture images, particularly when
trying to build images in emulated builds (e.g. armv7hf built on aarch64).

Moving the full build to single-arch solves this as the docker engine is
capable of chosing the right architecture from the manifest. Once some
of the builder issues are fixed, we should move to #2141

Relates-to: balena-io/balena-builder#1010
Change-type: patch

Dockerfile.template

@@ -1,24 +1,28 @@
 ARG ARCH=%%BALENA_ARCH%%
-
-# Used by livepush to support multi arch images in older
-# balenaOS with buggy platform support
-# see https://github.com/balena-os/balena-engine/issues/269
-ARG PREFIX=library
 ARG FATRW_VERSION=0.2.9
 
+
+FROM arm32v6/alpine:3.16 as alpine-rpi
+FROM arm32v7/alpine:3.16 as alpine-armv7hf
+FROM arm64v8/alpine:3.16 as alpine-aarch64
+FROM amd64/alpine:3.16 as alpine-amd64
+FROM i386/alpine:3.16 as alpine-i386
+
+FROM arm32v6/alpine:3.11 as procmail-rpi
+FROM arm32v7/alpine:3.11 as procmail-armv7hf
+FROM arm64v8/alpine:3.11 as procmail-aarch64
+FROM amd64/alpine:3.11 as procmail-amd64
+FROM i386/alpine:3.11 as procmail-i386
+
 ###################################################
 # Build the supervisor dependencies
 ###################################################
 FROM balenalib/${ARCH}-alpine-node:16-run as build-base
 
 ARG ARCH
-ARG PREFIX
 ARG FATRW_VERSION
 ARG FATRW_ARCHIVE="fatrw-${ARCH}.tar.gz"
 ARG FATRW_LOCATION="https://github.com/balena-os/fatrw/releases/download/v${FATRW_VERSION}/${FATRW_ARCHIVE}"
-# Sanity check to prevent a prefix for a non-official docker image being
-# inserted. Only 'library' and 'arm32v6' are allowed right now
-RUN for allowed in "library" "arm32v6"; do [ "${PREFIX}" = "${allowed}" ] && break; done
 
 WORKDIR /usr/src/app
 
@@ -63,7 +67,7 @@ RUN /setup-journal.sh
 # Extra dependencies. This uses alpine 3.11 as the
 # procmail package was removed on 3.12
 ###################################################
-FROM ${PREFIX}/alpine:3.11 as extra
+FROM procmail-${ARCH} as extra
 
 RUN apk add --update --no-cache procmail
 
@@ -71,7 +75,7 @@ RUN apk add --update --no-cache procmail
 # Image with the final production dependencies.
 # This image will also be be used for testing
 ###################################################
-FROM ${PREFIX}/alpine:3.16 as runtime-base
+FROM alpine-${ARCH} as runtime-base
 
 WORKDIR /usr/src/app
 

sync/init.ts

@@ -14,27 +14,6 @@ interface Opts {
 	arch?: string;
 }
 
-function getPathPrefix(arch: string) {
-	switch (arch) {
-		/**
-		 * Proper paths are
-		 * - armv6 - arm32v6
-		 * - armv7hf - arm32v7
-		 * - aarch64 - arm64v8
-		 * - amd64 - amd64
-		 * - i386 - i386
-		 *
-		 * We only set the prefix for v6 images since rpi devices are
-		 * the only ones that seem to have the issue
-		 * https://github.com/balena-os/balena-engine/issues/269
-		 */
-		case 'rpi':
-			return 'arm32v6';
-		default:
-			return 'library';
-	}
-}
-
 export async function initDevice(opts: Opts) {
 	const arch = opts.arch ?? (await device.getDeviceArch(opts.docker));
 	const image = `${opts.imageName}:${opts.imageTag}`;
@@ -42,7 +21,7 @@ export async function initDevice(opts: Opts) {
 	const buildCache = await device.readBuildCache(opts.address);
 
 	const stageImages = await device.performBuild(opts.docker, opts.dockerfile, {
-		buildargs: { ARCH: arch, PREFIX: getPathPrefix(arch) },
+		buildargs: { ARCH: arch },
 		t: image,
 		labels: { 'io.balena.livepush-image': '1', 'io.balena.architecture': arch },
 		cachefrom: (await device.getCacheFrom(opts.docker))