Substrate Raspberry PI cross-compile build

cross-build.sh

#!/bin/bash

# Run this script from the directory with the Cargo project.

docker run --rm -it \
	--env BINDGEN_EXTRA_CLANG_ARGS="--sysroot=/usr/arm-linux-gnueabihf -D__ARM_PCS_VFP -mfpu=vfp -mfloat-abi=hard" \
	--env CARGO_HOME=/home/rust/src/cargo_home \
	-v "$(pwd)":/home/rust/src <containter id> \
	cargo build --target=armv7-unknown-linux-gnueabihf --release

Dockerfile

# Put this file in the root of substrate / polkadot directory and build the image using	
# the following command:	
#	
#     docker build -t <container id> .	
#	
# you can pick <container id> yourself. For example: `johndoe/rpi-cross`.	
#	

FROM rust:latest

RUN dpkg --add-architecture armhf && \
    apt-get update && apt-get upgrade -y && \
    apt-get install -y aptitude && \
    aptitude install -y \
        gcc-arm-linux-gnueabihf \
        g++-arm-linux-gnueabihf \
        pkg-config \
        cmake \
        libssl-dev \
        git \
        clang \
        libclang-dev \
        libssl-dev:armhf

# Install nightly with w32-u-u and add arvm7 to stable
RUN rustup target add armv7-unknown-linux-gnueabihf
RUN rustup install nightly && \
    rustup target add wasm32-unknown-unknown --toolchain nightly &&\
    cargo +nightly install --git https://github.com/alexcrichton/wasm-gc --force

ENV CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER arm-linux-gnueabihf-gcc
ENV PKG_CONFIG_ALLOW_CROSS 1
ENV PKG_CONFIG_PATH /usr/lib/arm-linux-gnueabihf/pkgconfig/


# Disallow the `pkg-config` crate to look for the config for zlib, because build.rs of `libz-sys`
# gets confused and pulls the system-wide library (i.e. of the host) instead of the target when
# cross-compiling. This essentially leads to static linking of zlib.
#
# Alternatively, we can supply LIBZ_SYS_STATIC=1. Weirdly enough, installing libgtk-3-dev:armhf 
# also solves the problem somehow.   
#
# Here is the related issue: https://github.com/rust-lang/libz-sys/issues/49
ENV ZLIB_NO_PKG_CONFIG 1

# This is for compiling GUI apps.
# RUN aptitude install -y libasound2-dev:armhf libgtk-3-dev:armhf libsdl2-dev:armhf

RUN useradd rust --user-group --create-home --shell /bin/bash --groups sudo
WORKDIR /home/rust/src