Script to create Docker image with Alpine / MUSL toolchains

build-alpine-toolchains.sh

#!/bin/bash

# This script creates multiple musl toolchains for LLVM.
# These can be used directly to produce static Linux binaries.
# Pass the alpine version as a command line parameter
# (see https://alpinelinux.org/downloads/)
#
# Usage: bash build-alpine-toolchains.sh v3.20
#
# For example, to compile for x86_64
: '
clang --target=x86_64-alpine-linux-musl \
      --sysroot=/usr/x86_64-alpine-linux-musl/usr \
      --gcc-toolchain=/usr/x86_64-alpine-linux-musl/usr \
      -static test.c
'

set -eu

ALPINE_VERSION=$1

# Get apk binary (https://gitlab.alpinelinux.org/alpine/apk-tools)
APK=/tmp/apk.static
HOST_ARCH="$(uname -m)"
rm -f "${APK}"
wget -q "https://gitlab.alpinelinux.org/api/v4/projects/5/packages/generic/v2.12.14/${HOST_ARCH}/apk.static" -O "${APK}"
chmod +x "${APK}"

for ARCH in armhf armv7 aarch64 x86_64 x86; do
    # Create blank rootfs
    ROOTFS="/tmp/alpine-${ARCH}"
    rm -rf "${ROOTFS}" && mkdir "${ROOTFS}"

    # Add toolchain packages
    /tmp/apk.static add -q --no-scripts --no-cache --allow-untrusted --initdb \
        -X "https://dl-cdn.alpinelinux.org/alpine/${ALPINE_VERSION}/main" \
        --arch "${ARCH}" --root "${ROOTFS}" \
        linux-headers g++

    # Get GNU triple for the toolchain
    TRIPLE=$(ls "${ROOTFS}/usr/lib/gcc" | head -1)

    # Move toolchain to target directory
    rm -rf "/usr/${TRIPLE}" && mkdir -p "/usr/${TRIPLE}"
    mv "${ROOTFS}/usr" "${ROOTFS}/lib" "/usr/${TRIPLE}/"
    rm -rf "${ROOTFS}"

    echo "Created toolchain in /usr/${TRIPLE}"
done

# Cleanup
rm -f "${APK}"