[Cin] AppImage's new runtime

[Andrew Randrianasulu]

https://github.com/AppImage/type2-runtime/issues/77

I think I fixed it, now it builds inside Alpine chroot and correctly copied
out before chroot deleted (debuggin this was ... slow)

I see it uses libfuse3 so hopefully there will be no need for libfuse2
workaround on new Debian 11, etc.

But I have not tried to use this runtime part anywhere yet.

Build takes around 400 mb in /tmp
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