Create tar.gz in a reproducible way

[bmwiedemann]

Create tar.gz in a reproducible way
by sorting entries, overriding UID, mtime
and using gzip -n to not add a timestamp in .gz header

See https://reproducible-builds.org/ for why this is good.

[L1L1]

This does not work on Ubuntu 18.04 (and probably others) and breaks the compilation. Some modifications will be needed.

[bmwiedemann]

hmm. how does it fail? I guess, the tar is older and does not have the sort option?

[L1L1]

During make I get:

  TAR      dot_cardpeek_dir
tar: --clamp-mtime needs a date specified using --mtime
Try 'tar --help' or 'tar --usage' for more information.

Removing --clamp-mtime fixes the problem

[bmwiedemann]

try this instead: --mtime @1 --clamp-mtime

This has reproducible build results without influences from timestamps of dirs touched during build.

[L1L1]

OK that works on Ubuntu and MacOS.