[tlbuild] zstd as package compressor

[Henri Menke]

Dear list,

On TeX.SX a question came up “Why texlive installation is so slow?” and
Norbert answered mentioning several points [1].

One point that Norbert mentioned was decompression speed.  This reminded
me that the Arch Linux distribution recently switched their compression
format to Zstandard for exactly that reason [2].  Quoting from their
experience:

> Recompressing all packages to zstd with our options yields a total
> ~0.8% increase in package size on all of our packages combined, but
> the decompression time for all packages saw a ~1300% speedup.

This is a massive speedup and it would be great if TeX Live could make
use of this.  Of course there are different trade-offs to consider, such
as the DVD size limit.

I totally understand that switching to a different compression is not an
easy task at all, but it might still be worthwhile to have a discussion.

Cheers, Henri

[1] https://tex.stackexchange.com/questions/527364
[2] https://www.archlinux.org/news/now-using-zstandard-instead-of-xz-for-package-compression/