Update flatpak build

[Parnassius]

This updates several things in the flatpak build:

• The flatpak dependencies are automatically installed using the --install-deps-from=flathub parameter of flatpak-builder, instead of installing them explicitly.
• The runtime version has been updated to 24.08. This removes the need to pin flathub/shared-modules to an older commit.
• --socket=x11 has been replaced by --socket=fallback-x11. This has no effect on x11 sessions, but removes the unneeded x11 socket on wayland sessions.
• Some unsed parts have been removed, including SDL2_image (the dependency is already included in the standard flatpak runtime, it just needs a couple of symlinks for it to be detected by dotnet).
• I've also updated ffmpeg to the latest version of the 5.1 series.
• A desktop file is included to make it possible to open SysDVR from the GUI menus, without having to open a terminal.

I've tested this with the latest sysmodule release and it's working fine on both network and usb modes.

[exelix11]

Thank you, this is looking great.
I only have one question, did you look into the possibility of using org.freedesktop.Platform.ffmpeg-full instead of building it ? The reason is that 90% of the build time of the flatpak is just ffmpeg, getting rid of that step would make it much faster.

[Parnassius]

Yes, unfortunately the ffmpeg version provided by that extension doesn't match what's required by the the version of FFmpeg.AutoGen currently used. That wrapper requires 5.1 (libavutil57, libavcodec59, ...), while org.freedesktop.Platform.ffmpeg-full only provides ffmpeg 6.1 (libavutil58, libavcodec60, ...) on 23.08, or ffmpeg 7.x (libavutil59, libavcodec61, ...) on 24.08.

If the wrapper can be updated to use a newer version, then removing the custom built ffmpeg from the manifest and replacing it with org.freedesktop.Platform.ffmpeg-full should be quite easy.

[exelix11]

I see. For now i don't plan on updating the wrapper cause it would mean also figuring out updates on all other platofrms too.

[Parnassius]

Yeah, I thought it wasn't really an easy task. Anyway it can be revisited in the future