chore(linux): Improved Flatpak builds.

Author: Skyost

flatpak/Dockerfile

@@ -1,5 +1,13 @@
 FROM ubuntu:24.04
 
+ARG UID=1000
+ARG GID=1000
+
+RUN groupadd --non-unique -g ${GID} auser && \
+    useradd --non-unique --no-create-home -u ${UID} -g ${GID} auser || \
+    usermod -u ${UID} -g ${GID} $(getent passwd ${UID} | cut -d: -f1) && \
+    groupmod -g ${GID} $(getent group ${GID} | cut -d: -f1)
+
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive TZ=Europe apt-get -y install tzdata
 RUN apt-get -y install tree curl file git unzip xz-utils zip clang cmake ninja-build pkg-config libgtk-3-dev liblzma-dev
 RUN apt-get -y install libsecret-1-dev libpolkit-gobject-1-dev
@@ -9,8 +17,23 @@ RUN flatpak install -y org.freedesktop.Sdk/x86_64/25.08
 RUN flatpak install -y org.freedesktop.Platform/x86_64/25.08
 RUN flatpak install -y flathub org.freedesktop.appstream-glib
 
-RUN git clone https://github.com/flutter/flutter.git -b stable /opt/flutter
-ENV PATH="/opt/flutter/bin:${PATH}"
-RUN git config --global --add safe.directory /opt/flutter
-RUN flutter --disable-analytics && flutter upgrade
-RUN chown -R "$(id -u):$(id -g)" /opt/flutter
+RUN mkdir -p /home/auser
+RUN chown -R ${UID}:${GID} /home/auser
+USER ${UID}
+ENV HOME=/home/auser
+WORKDIR /home/auser
+
+RUN git clone https://github.com/flutter/flutter.git -b stable /home/auser/flutter
+ENV PATH="$PATH:/home/auser/flutter/bin:/home/auser/flutter/bin/cache/dart-sdk/bin"
+RUN flutter --disable-analytics
+RUN flutter config --enable-linux-desktop \
+                   --no-enable-windows-desktop \
+                   --no-enable-macos-desktop \
+                   --no-enable-web \
+                   --no-enable-android \
+                   --no-enable-ios
+RUN flutter precache
+RUN flutter upgrade
+RUN chown -R ${UID}:${GID} /home/auser/flutter
+
+RUN git config --global --add safe.directory /home/auser/flutter