Cross compile workflow

[ssssam]

I want to build for ARM devices, initially targetting Organelle 1.

Ideal approach might be to use rust-embedded/cross tool, which uses prebuilt Ubuntu containers to run Rust toolchain.

As of cross 0.2.1 (15/11/2021), the default command cross build --target armv7-unknown-linux-musleabihf fails to build 'alsa-sys' crate because the sysroot doesn't contain libasound headers. Related issues:

• Wishlist: Add a feature to support installing packages in the Docker image when cross runs cross-rs/cross#281
• Unable to add packages for other architectures cross-rs/cross#149

The workaround is to use custom Docker images as a build base instead of the default ones, so we might build our own image and add this in Cross.toml:

[target.aarch64-unknown-linux-gnu]
image = "my/image:tag"

[ssssam]

I tried using a custom Docker image.

> cat docker/Dockerfile.arm 
FROM rustembedded/cross:armv7-unknown-linux-gnueabihf-0.2.1

RUN dpkg --add-architecture armhf && \
    apt-get update && \
    apt-get install --assume-yes libasound2-dev:armhf

ENV PKG_CONFIG_PATH=/usr/lib/arm-linux-gnueabihf/pkgconfig

> cat Cross.toml 
[target.armv7-unknown-linux-gnueabihf]
image = "boucle/build:latest"

Build the image:

podman build -f ./docker/Dockerfile.arm -t boucle/build

This results in a successful shared build of boucle_organelle binary, linked against GLIBC 2.23, which actually seems to work on the Organelle OS which uses 2.22. Maybe this is good enough for now.