fix: working armv6hf docker image for cross-compiling

Author: gpajot

contrib/Dockerfile

@@ -2,7 +2,7 @@
 # Build the docker image from the root of the project with the following command :
 # $ docker build -t librespot-cross -f contrib/Dockerfile .
 #
-# The resulting image can be used to build librespot for linux x86_64, armhf(with support for armv6hf), armel, mipsel, aarch64
+# The resulting image can be used to build librespot for linux x86_64, armhf, armel, mipsel, aarch64
 # $ docker run -v /tmp/librespot-build:/build librespot-cross
 #
 # The compiled binaries will be located in /tmp/librespot-build
@@ -13,8 +13,6 @@
 # $ docker run -v /tmp/librespot-build:/build librespot-cross cargo build --release --target arm-unknown-linux-gnueabi --no-default-features --features alsa-backend
 # $ docker run -v /tmp/librespot-build:/build librespot-cross cargo build --release --target aarch64-unknown-linux-gnu --no-default-features --features alsa-backend
 
-# $ docker run -v /tmp/librespot-build:/build librespot-cross contrib/docker-build-pi-armv6hf.sh
-
 FROM debian:stretch
 
 RUN dpkg --add-architecture arm64
@@ -40,10 +38,6 @@ RUN mkdir /.cargo && \
     echo '[target.arm-unknown-linux-gnueabi]\nlinker = "arm-linux-gnueabi-gcc"' >> /.cargo/config && \
     echo '[target.mipsel-unknown-linux-gnu]\nlinker = "mipsel-linux-gnu-gcc"' >> /.cargo/config
 
-RUN mkdir /build && \
-    mkdir /pi-tools && \
-    curl -L https://github.com/raspberrypi/tools/archive/648a6eeb1e3c2b40af4eb34d88941ee0edeb3e9a.tar.gz | tar xz --strip-components 1 -C /pi-tools
-
 ENV CARGO_TARGET_DIR /build
 ENV CARGO_HOME /build/cache
 ENV PKG_CONFIG_ALLOW_CROSS=1

contrib/cross-compile-armv6hf/Dockerfile

@@ -0,0 +1,49 @@
+# Cross compilation environment for librespot in armv6hf.
+# Build the docker image from the root of the project with the following command:
+# $ docker build -t librespot-cross-armv6hf -f contrib/cross-compile-armv6hf/Dockerfile .
+#
+# The resulting image can be used to build librespot for armv6hf:
+# $ docker run -v /tmp/librespot-build-armv6hf:/build librespot-cross-armv6hf
+#
+# The compiled binary will be located in /tmp/librespot-build-armv6hf/arm-unknown-linux-gnueabihf/release/librespot
+
+FROM --platform=linux/amd64 ubuntu:18.04
+
+# Install common packages.
+RUN apt-get update
+RUN apt-get install -y -qq git curl build-essential libasound2-dev libssl-dev libpulse-dev libdbus-1-dev
+
+# Install armhf packages.
+RUN echo "deb [arch=armhf] http://ports.ubuntu.com/ubuntu-ports/ bionic main" | tee -a /etc/apt/sources.list
+RUN apt-get update
+RUN apt-get download libasound2:armhf libasound2-dev:armhf libssl-dev:armhf libssl1.1:armhf
+RUN mkdir /sysroot && \
+    dpkg -x libasound2_*.deb /sysroot/ && \
+    dpkg -x libssl-dev*.deb /sysroot/ && \
+    dpkg -x libssl1.1*.deb /sysroot/ && \
+    dpkg -x libasound2-dev*.deb /sysroot/
+
+# Install rust.
+RUN curl https://sh.rustup.rs -sSf | sh -s -- -y
+ENV PATH="/root/.cargo/bin/:${PATH}"
+RUN rustup target add arm-unknown-linux-gnueabihf
+RUN mkdir /.cargo && \
+    echo '[target.arm-unknown-linux-gnueabihf]\nlinker = "arm-linux-gnueabihf-gcc"' >> /.cargo/config
+
+# Install Pi tools for armv6.
+RUN mkdir /pi && \
+    git -C /pi clone --depth=1 https://github.com/raspberrypi/tools.git
+
+# Build env variables.
+ENV CARGO_TARGET_DIR /build
+ENV CARGO_HOME /build/cache
+ENV PATH="/pi/tools/arm-bcm2708/arm-linux-gnueabihf/bin:${PATH}"
+ENV PKG_CONFIG_ALLOW_CROSS=1
+ENV PKG_CONFIG_PATH_arm-unknown-linux-gnueabihf=/usr/lib/arm-linux-gnueabihf/pkgconfig/
+ENV C_INCLUDE_PATH=/sysroot/usr/include
+ENV OPENSSL_LIB_DIR=/sysroot/usr/lib/arm-linux-gnueabihf
+ENV OPENSSL_INCLUDE_DIR=/sysroot/usr/include/arm-linux-gnueabihf
+
+ADD . /src
+WORKDIR /src
+CMD ["/src/contrib/cross-compile-armv6hf/docker-build.sh"]

contrib/cross-compile-armv6hf/docker-build.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -eux
+
+PI1_TOOLS_DIR="/pi/tools/arm-bcm2708/arm-linux-gnueabihf"
+
+PI1_LIB_DIRS=(
+  "$PI1_TOOLS_DIR/arm-linux-gnueabihf/sysroot/lib"
+  "$PI1_TOOLS_DIR/arm-linux-gnueabihf/sysroot/usr/lib"
+  "/sysroot/usr/lib/arm-linux-gnueabihf"
+  "/sysroot/lib/arm-linux-gnueabihf"
+)
+export RUSTFLAGS="-C linker=$PI1_TOOLS_DIR/bin/arm-linux-gnueabihf-gcc ${PI1_LIB_DIRS[*]/#/-L}"
+
+cargo build --release --target arm-unknown-linux-gnueabihf --no-default-features --features "alsa-backend"