Emulated-compilation of Docker images for another target platform with Python packages from source

build.sh

#!/bin/sh

# Requires binfmt to support linux/arm64 (or any other target).
docker buildx build --platform linux/arm64 .

Dockerfile

# syntax=docker/dockerfile:experimental

# Compile all dependencies in a separate build environment. Note that the
# cache is copied to /cache as a final step, because the actual cache folder
# is an external mount.
FROM --platform=$TARGETPLATFORM python:3.8-alpine3.13 as buildenv

COPY requirements_base.txt requirements.txt ./

RUN --mount=type=cache,target=/root/.cache \
	apk update && \
	apk add --upgrade \
		build-base \
		ca-certificates \
		curl \
		freetype-dev \
		g++ \
		jpeg-dev \
		lapack-dev \
		less \
		libexecinfo-dev \
		libgcc \
		libgfortran \
		libgomp \
		libpng-dev \
		make \
		musl \
		openblas-dev \
		openssl \
		rsync \
		wget \
		zlib-dev && \
	pip install --upgrade pip wheel && \
	pip install -r requirements_base.txt && \
	pip install -r requirements.txt && \
	cp -r /root/.cache /cache

# Build the final image.
FROM --platform=$TARGETPLATFORM python:3.8-alpine3.13 as image

COPY --from=buildenv /cache /root/.cache

COPY requirements_base.txt requirements.txt ./

RUN apk update && \
	apk add --upgrade \
		lapack \
		libgomp \
		libjpeg \
		libstdc++ \
		openblas && \
	pip install --upgrade pip wheel && \
	pip install -r requirements_base.txt && \
	pip install -r requirements.txt && \
	rm -f requirements_base.txt && \
	rm -f requirements.txt && \
	rm -rf /root/.cache && \
	rm -rf /var/cache

COPY . /src

WORKDIR /src

Yes that makes sense, I'm using emulation now and it works (but slow as you mentioned). Just wanted to add a note here in case anyone else is looking for the same thing, since this is the closest example I could find!