Update appimagetool to use newer type2-runtime

[Drsheppard01]

I think it is very important to implement this feature now, because many projects rely on pkg2appimage, but we don't have any appimages created using runtime (at least I haven't seen any). Also pkg2appimage will be the first build tool to implement this feature

[probonopd]

I don't understand what you mean by "this feature". What are "runtime dealing functions"?

Every type-2 AppImage consists of a small AppImage runtime (the executable ELF binary), to the end of which a compressed (usually zstd squashfs) filesystem image is appended.

[Drsheppard01]

I mean being able to run AppImage on machines without glibc. If I understand it correctly, adding type2-runtime will help me to run any AppImage on any system

[probonopd]

Yes, if pkg2appimage would use type2-runtime instead of the older runtime then the AppImage mounting code would not need glibc. (If this appimagetool would be used, then it would use the type2-runtime.) The contents of the AppImage would still require glibc though, unless the logic there would also be changed to bundle everything.

The proper solution is to get application developers to release and support official AppImages of their applications. pkg2appimage is just a workaround that basically should not be used.

[Drsheppard01]

I know you often dislike the comparison of AppImage to Flatpak, but their build machine has the ability to repackage from almost any format, if you add all available formats into one (like flatpak2appdir or snap2appdir, rpm2appdir) and make a comprehensive build system, it could help AppImage's development

[probonopd]

AppImages should not be made by "repackaging" because it usually results in low-quality, unsupported software. The AppImage format is intended for the developers of applications who want to make officically produced and officially supported AppImages.