Bundle static versions of desktop-file-validate and zsyncmake

[probonopd]

To maintain drop-in compatibility, we also need to ship like we did in AppImageKit's appimagetool:

• usr/bin/desktop-file-validate
• usr/bin/zsyncmake

(fwiw, https://github.com/probonopd/static-tools/releases/tag/continuous has those, built statically on Alpine Linux.)

[TheAssassin]

We should consider making zsync2 a core project again. Then we could utilize libzsync2 directly instead of having to build and ship separate tools.

Note: this just affects zsync2 itself, not AppImageUpdate.

[probonopd]

utilize libzsync2

Maybe after 1.0

[TheAssassin]

Since we want to make this repository be as self-contained as possible (except for AppImage core projects), I'll add build scripts for these inspired by the code in your repository just as we've done for mksquashfs. This is going to increase the build times slightly for now, but that is acceptable to me.

Is there a library for checking desktop entries, too?

[probonopd]

Agree on making this repo as self-contained as possible (except for AppImage core projects). Mentioned static-tools only as a reference in case it is helpful.

I don't know a library for checking desktop entries but it shouldn't be all too hard to convert
https://gitlab.freedesktop.org/xdg/desktop-file-utils/-/blob/master/src/validate.c
into one. But then, we'd have to maintain it, so not sure whether it'd be worth the effort.

[rodlie]

Would appreciate if you removed the need for desktop-file-validate, I upgraded appimagetool on my build server today and my build broke due to this (yes, my previous appimagetool was old, 2023-03-08, btw why have you wiped the git history?).

For various reasons I won't discuss I'm unable install desktop-file-validate, so I had to make a dummy file to work around this.

[probonopd]

Well, I think we need to bundle a static build of desktop-file-validate (and other similar needed tools). Would that satisfy your use case @rodlie?