The latest release of appimagetool bundles a new enough version of
mksquashfs. We had been building a fork of mksquashfs but all the
relevant patches there had been upstreamed.
Note: we still need a wrapper when calling mksquashfs, as appimagetool
calls it with "-mkfs-time 0" and we have the SOURCE_DATE_EPOCH env var
set; and these two would conflict.
Two ways to fix: either unset SOURCE_DATE_EPOCH for that context, or
build a wrapper that removes the "-mkfs-time 0". The former would be
cleaner but for some reason I did not manage to build reproducibly
that way. The latter seems to work.
related:
- https://github.com/AppImage/AppImageKit/issues/929#issuecomment-580769875
> Now official squashfs 4.4 makes reproducible images by default
- https://github.com/AppImage/AppImageKit/pull/996
