Modernize and fix build system

ci/Dockerfile

@@ -1,8 +1,7 @@
 # these args are available *only* for the FROM call
-ARG DOCKER_ARCH
-ARG DIST
+ARG RELEASE
 
-FROM $DOCKER_ARCH/ubuntu:$DIST
+FROM ubuntu:$RELEASE
 
 # we need to repeat all args from above which we need during build and runtime to make them available
 ARG ARCH
@@ -12,9 +11,9 @@ ENV CI=1
 
 COPY ./install-deps.sh /
 # see above, for build time we need to pass the args manually (using ENV does not work)
-RUN bash -xe install-deps.sh
+RUN bash -xe /install-deps.sh
 
 # create unprivileged user for non-build-script use of this image
 # build-in-docker.sh will likely not use this one, as it enforces the caller's uid inside the container
-RUN adduser --system --group build
+RUN useradd build
 USER build

ci/build-docker-image.sh

@@ -1,12 +1,11 @@
 #! /bin/bash
 
-if [[ "$DIST" == "" ]] || [[ "$ARCH" == "" ]]; then
-    echo "Usage: env ARCH=... DIST=... bash $0"
+if [[ "${ARCH:-}" == "" ]] || [[ "${RELEASE:-}" == "" ]]; then
+    echo "Usage: env ARCH=... RELEASE=... bash $0"
     exit 1
 fi
 
-set -x
-set -e
+set -euo pipefail
 
 # the other script sources this script, therefore we have to support that use case
 if [[ "${BASH_SOURCE[*]}" != "" ]]; then
@@ -15,30 +14,21 @@ else
     this_dir="$(readlink -f "$(dirname "$0")")"
 fi
 
-case "$ARCH" in
-    x86_64)
-        export DOCKER_ARCH=amd64
-        ;;
-    *)
-        export DOCKER_ARCH="$ARCH"
-        ;;
-esac
-
-image=quay.io/appimage/libappimage-build:"$DIST"-"$ARCH"
+image=quay.io/appimage/libappimage-build:"$RELEASE"
 
 extra_build_args=()
-if [[ "$NO_PULL" == "" ]]; then
+if [[ "${NO_PULL:-}" == "" ]]; then
     # speed up build by pulling last built image from quay.io and building the docker file using the old image as a base
     docker pull "$image" || true
     extra_build_args=(--cache-from "$image")
 fi
 
 # if the image hasn't changed, this should be a no-op
 docker build \
+    --platform "$platform" \
     --pull \
-    --build-arg DOCKER_ARCH \
     --build-arg ARCH \
-    --build-arg DIST \
+    --build-arg RELEASE \
     -t "$image" \
     "${extra_build_args[@]}" \
     "$this_dir"
@@ -48,7 +38,7 @@ docker build \
 # rebuilt anyway
 # credentials shall only be available on (protected) master branch
 set +x
-if [[ "$DOCKER_USERNAME" != "" ]]; then
+if [[ "${DOCKER_USERNAME:-}" != "" ]]; then
     echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin quay.io
     docker push "$image"
 fi

ci/build-in-docker.sh

@@ -1,31 +1,51 @@
 #! /bin/bash
 
-if [[ "$DIST" == "" ]] || [[ "$ARCH" == "" ]]; then
-    echo "Usage: env ARCH=... DIST=... bash $0"
+if [[ "${ARCH:-}" == "" ]] || [[ "${RELEASE:-}" == "" ]]; then
+    echo "Usage: env ARCH=... RELEASE=... bash $0"
     exit 1
 fi
 
-set -x
-set -e
+set -euo pipefail
 
-cd "$(readlink -f "$(dirname "$0")")"
-
-if [[ "$DIST" != appimagebuild* ]]; then
-    # sets variables $image
-    source build-docker-image.sh
+# the other script sources this script, therefore we have to support that use case
+if [[ "${BASH_SOURCE[*]}" != "" ]]; then
+    this_dir="$(readlink -f "$(dirname "${BASH_SOURCE[0]}")")"
 else
-    image=quay.io/appimage/appimagebuild:centos7-"$ARCH"
-    docker pull "$image"
+    this_dir="$(readlink -f "$(dirname "$0")")"
 fi
 
+case "$ARCH" in
+    x86_64)
+        platform=linux/amd64
+        ;;
+    i686)
+        platform=linux/i386
+        ;;
+    armhf)
+        platform=linux/arm/v7
+        ;;
+    aarch64)
+        platform=linux/arm64/v8
+        ;;
+    *)
+        echo "unknown architecture: $ARCH"
+        exit 2
+        ;;
+esac
+
+cd "$(readlink -f "$(dirname "$0")")"
+
+# sets variables $image
+source build-docker-image.sh
+
 DOCKER_OPTS=()
 # fix for https://stackoverflow.com/questions/51195528/rcc-error-in-resource-qrc-cannot-find-file-png
-if [ "$CI" != "" ]; then
+if [ "${CI:-}" != "" ]; then
     DOCKER_OPTS+=("--security-opt" "seccomp:unconfined")
 fi
 
 # only if there's more than 3G of free space in RAM, we can build in a RAM disk
-if [[ "$GITHUB_ACTIONS" != "" ]]; then
+if [[ "${GITHUB_ACTIONS:-}" != "" ]]; then
     echo "Building on GitHub actions, which does not support --tmpfs flag -> building on regular disk"
 elif [[ "$(free -m  | grep "Mem:" | awk '{print $4}')" -gt 3072 ]]; then
     echo "Host system has enough free memory -> building in RAM disk"

ci/install-deps.sh

@@ -1,37 +1,14 @@
 #! /bin/bash
 
-set -e
+set -euo pipefail
 
-if [[ "$ARCH" == "" ]]; then
-    echo "Usage: env ARCH=... bash $0"
-    exit 2
-fi
-
-if [[ "$CI" == "" ]]; then
+if [[ "${CI:-}" == "" ]]; then
     echo "Caution: this script is supposed to run inside a (disposable) CI environment"
     echo "It will alter a system, and should not be run on workstations or alike"
     echo "You can export CI=1 to prevent this error from being shown again"
     exit 3
 fi
 
-case "$ARCH" in
-    x86_64|i386|armhf|arm64)
-        ;;
-    *)
-        echo "Error: unsupported architecture: $ARCH"
-        exit 4
-        ;;
-esac
-
-case "$DIST" in
-    bionic|focal)
-        ;;
-    *)
-        echo "Error: unsupported distribution: $DIST"
-        exit 5
-        ;;
-esac
-
 set -x
 
 packages=(
@@ -58,29 +35,11 @@ packages=(
     lcov
     gcovr
     libboost-dev
+    g++-multilib
 )
 
-# install gcc-10 (supports C++17 with std::filesystem properly)
-if [[ "$DIST" == "bionic" ]]; then
-    apt-get update
-    apt-get install --no-install-recommends -y software-properties-common
-    add-apt-repository -y ppa:ubuntu-toolchain-r/test
-    packages+=(g++-10-multilib)
-else
-    packages+=(g++-multilib)
-fi
-
 # make sure installation won't hang on GitHub actions
 export DEBIAN_FRONTEND=noninteractive
 
 apt-get update
 apt-get -y --no-install-recommends install "${packages[@]}"
-
-# install more recent CMake version
-wget https://artifacts.assassinate-you.net/prebuilt-cmake/continuous/cmake-v3.24.1-ubuntu_"$DIST"-"$ARCH".tar.gz -qO- | \
-    tar xz -C/usr/local --strip-components=1
-
-# g++-10 should be used by default
-if [[ "$DIST" == "bionic" ]]; then
-    update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++-10 9999
-fi