tool: Add scripts and dockerfiles for cross-compiling linux arm64

tool/Dockerfile.build

@@ -0,0 +1,19 @@
+FROM debian:stable-slim
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    # dependencies to install flutter
+    git curl unzip ca-certificates \
+    # dependencies to build for linux
+    clang cmake ninja-build pkg-config libgtk-3-dev \
+    # dependencies for the app
+    libayatana-appindicator3-dev
+
+ARG FLUTTER_VERSION
+RUN git clone -b $FLUTTER_VERSION https://github.com/flutter/flutter /flutter
+ENV PATH=$PATH:/flutter/bin
+RUN flutter doctor -v
+RUN flutter precache --linux
+
+ADD docker/build.sh /build.sh
+CMD /build.sh

tool/build-neon.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+set -euxo pipefail
+cd "$(dirname "$0")/.."
+
+arches=("amd64" "arm64")
+flutter_version="$(jq ".flutterSdkVersion" -r < .fvm/fvm_config.json | cut -d "@" -f 1)"
+
+function cleanup() {
+  cd packages/neon
+  rm -rf .packages .dart_tool
+  fvm flutter pub get
+}
+trap cleanup EXIT
+
+for arch in "${arches[@]}"; do
+  docker buildx build \
+  --platform "linux/$arch" \
+  --progress plain \
+  -t "nextcloud-neon-build:$arch"  \
+  --build-arg="FLUTTER_VERSION=$flutter_version" \
+  -f tool/Dockerfile.build \
+  ./tool
+
+  docker run \
+  --platform "linux/$arch" \
+  --rm -it \
+  -e "ORIGINAL_USER=$(id -u)" \
+  -e "ORIGINAL_GROUP=$(id -g)" \
+  -v "$(pwd):/src" \
+  "nextcloud-neon-build:$arch"
+done

tool/docker/build.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -euxo pipefail
+
+function cleanup() {
+  chown -R "$ORIGINAL_USER:$ORIGINAL_GROUP" .
+}
+trap cleanup EXIT
+
+cd /src/packages/neon
+
+rm -rf .packages .dart_tool
+flutter build linux