Add scripts for continuous integration

.gitlab/ci/build-host.sh:
Add script to be run in a container with access to qemu.
It is a slight modification of arch-boxes' build-host.sh script to cater to the specific archiso requirements.

.gitlab/ci/build-inside-vm.sh:
Add script to be run in virtualized environment, established by build-host.sh.
This script builds the actual archiso profiles and creates checksum for the resulting image files.

.gitlab/ci/build-host.sh

+#!/bin/bash
+# build-host.sh runs build-inside-vm.sh in a qemu VM running the latest Arch installer iso
+#
+# nounset: "Treat unset variables and parameters [...] as an error when performing parameter expansion."
+# errexit: "Exit immediately if [...] command exits with a non-zero status."
+set -o nounset -o errexit
+readonly MIRROR="https://mirror.pkgbuild.com"
+
+function init() {
+  readonly ORIG_PWD="${PWD}"
+  readonly OUTPUT="${PWD}/output"
+  readonly TMPDIR="$(mktemp --dry-run --directory --tmpdir="${PWD}/tmp")"
+  mkdir -p "${OUTPUT}" "${TMPDIR}"
+
+  cd "${TMPDIR}"
+}
+
+# Do some cleanup when the script exits
+function cleanup() {
+  rm -rf "${TMPDIR}"
+  jobs -p | xargs --no-run-if-empty kill
+}
+trap cleanup EXIT
+
+# Use local Arch iso or download the latest iso and extract the relevant files
+function prepare_boot() {
+  if LOCAL_ISO="$(ls "${ORIG_PWD}/"archlinux-*-x86_64.iso 2>/dev/null)"; then
+    echo "Using local iso: ${LOCAL_ISO}"
+    ISO="${LOCAL_ISO}"
+  fi
+
+  if [ -z "${LOCAL_ISO}" ]; then
+    LATEST_ISO="$(curl -fs "${MIRROR}/iso/latest/" | grep -Eo 'archlinux-[0-9]{4}\.[0-9]{2}\.[0-9]{2}-x86_64.iso' | head -n 1)"
+    if [ -z "${LATEST_ISO}" ]; then
+      echo "Error: Couldn't find latest iso'"
+      exit 1
+    fi
+    curl -fO "${MIRROR}/iso/latest/${LATEST_ISO}"
+    ISO="${PWD}/${LATEST_ISO}"
+  fi
+
+  # We need to extract the kernel and initrd so we can set a custom cmdline:
+  # console=ttyS0, so the kernel and systemd sends output to the serial.
+  xorriso -osirrox on -indev "${ISO}" -extract arch/boot/x86_64 .
+  ISO_VOLUME_ID="$(xorriso -indev "${ISO}" |& awk -F : '$1 ~ "Volume id" {print $2}' | tr -d "' ")"
+}
+
+function start_qemu() {
+  # Used to communicate with qemu
+  mkfifo guest.out guest.in
+  # We could use a sparse file but we want to fail early
+  fallocate -l 8G scratch-disk.img
+
+  { qemu-system-x86_64 \
+    -machine accel=kvm:tcg \
+    -smp "$(nproc)" \
+    -m 4096 \
+    -net nic \
+    -net user \
+    -kernel vmlinuz-linux \
+    -initrd initramfs-linux.img \
+    -append "archisobasedir=arch archisolabel=${ISO_VOLUME_ID} ip=dhcp net.ifnames=0 console=ttyS0 mirror=${MIRROR}" \
+    -drive file=scratch-disk.img,format=raw,if=virtio \
+    -drive file="${ISO}",format=raw,if=virtio,media=cdrom,read-only \
+    -virtfs "local,path=${ORIG_PWD},mount_tag=host,security_model=none" \
+    -monitor none \
+    -serial pipe:guest \
+    -nographic || kill "${$}"; } &
+
+  # We want to send the output to both stdout (fd1) and fd10 (used by the expect function)
+  exec 3>&1 10< <(tee /dev/fd/3 <guest.out)
+}
+
+# Wait for a specific string from qemu
+function expect() {
+  local length="${#1}"
+  local i=0
+  local timeout="${2:-30}"
+  # We can't use ex: grep as we could end blocking forever, if the string isn't followed by a newline
+  while true; do
+    # read should never exit with a non-zero exit code,
+    # but it can happen if the fd is EOF or it times out
+    IFS= read -r -u 10 -n 1 -t "${timeout}" c
+    if [ "${1:${i}:1}" = "${c}" ]; then
+      i="$((i + 1))"
+      if [ "${length}" -eq "${i}" ]; then
+        break
+      fi
+    else
+      i=0
+    fi
+  done
+}
+
+# Send string to qemu
+function send() {
+  echo -en "${1}" >guest.in
+}
+
+function main() {
+  init
+  prepare_boot
+  start_qemu
+
+  # Login
+  expect "archiso login:"
+  send "root\n"
+  expect "# "
+
+  # Switch to bash and shutdown on error
+  send "bash\n"
+  expect "# "
+  send "trap \"shutdown now\" ERR\n"
+  expect "# "
+
+  # Prepare environment
+  send "mkdir /mnt/project && mount -t 9p -o trans=virtio host /mnt/project -oversion=9p2000.L\n"
+  expect "# "
+  send "mkfs.ext4 /dev/vda && mkdir /mnt/scratch-disk/ && mount /dev/vda /mnt/scratch-disk && cd /mnt/scratch-disk\n"
+  expect "# "
+  send "cp -a /mnt/project/{.gitlab,archiso,configs,scripts} .\n"
+  expect "# "
+  send "mkdir pkg && mount --bind pkg /var/cache/pacman/pkg\n"
+  expect "# "
+
+  # Wait for pacman-init
+  send "until systemctl is-active pacman-init; do sleep 1; done\n"
+  expect "# "
+
+  # Explicitly lookup mirror address as we'd get random failures otherwise during pacman
+  send "curl -sSo /dev/null ${MIRROR}\n"
+  expect "# "
+
+  # Install required packages
+  send "pacman -Sy --noconfirm qemu-headless jq dosfstools e2fsprogs libisoburn mtools squashfs-tools\n"
+  expect "# "
+
+  ## Start build and copy output to local disk
+  send "bash -x ./.gitlab/ci/build-inside-vm.sh ${PROFILE}\n "
+  expect "# " 1000 # mksquashfs can take a long time
+  send "cp -r --preserve=mode,timestamps output /mnt/project/tmp/$(basename "${TMPDIR}")/\n"
+  expect "# " 60
+  mv output/* "${OUTPUT}/"
+
+  # Shutdown the VM
+  send "shutdown now\n"
+  wait
+}
+main

.gitlab/ci/build-inside-vm.sh

+#!/usr/bin/env bash
+#
+# This script is run within a virtual environment to build the available archiso profiles and create checksum files for
+# the resulting images.
+# The script needs to be run as root and assumes $PWD to be the root of the repository.
+
+readonly orig_pwd="${PWD}"
+readonly output="${orig_pwd}/output"
+readonly tmpdir="$(mktemp --dry-run --directory --tmpdir="${orig_pwd}/tmp")"
+
+cleanup() {
+  # clean up temporary directories
+  if [ -n "${tmpdir:-}" ]; then
+    rm -rf "${tmpdir}"
+  fi
+}
+
+create_checksums() {
+  # create checksums for a file
+  # $1: a file
+  sha256sum "${1}" >"${1}.sha256"
+  sha512sum "${1}" >"${1}.sha512"
+  b2sum "${1}" >"${1}.b2"
+  if [ -n "${SUDO_UID:-}" ]; then
+    chown "${SUDO_UID}:${SUDO_GID}" "${1}"{,.b2,.sha{256,512}}
+  fi
+}
+
+run_mkarchiso() {
+  # run mkarchiso
+  # $1: template name
+  mkdir -p "${output}/${1}" "${tmpdir}/${1}"
+  ./archiso/mkarchiso -o "${output}/${1}" -w "${tmpdir}/${1}" -v "configs/${1}"
+  create_checksums "${output}/${1}/"*.iso
+}
+
+trap cleanup EXIT
+
+run_mkarchiso "${1}"