[tlbuild] zstd as package compressor

[Simon Dales]

On Wed, 2020-02-19 at 12:16 +0100, Johannes Hielscher wrote:
> Cumulative percentages: 
> perl: 67%
> xz: 11%
> kpsewhich: 8%

Were tlmgr be rewritten in lua then the script percentage would be
smaller. I re-wrote an unrelated perl script in lua and it went 10*
quicker. But even with a lua re-write there is still xz/zstd/... and
kpsewhich. Ultimately it's your disk speed.

However are you, or I, going to port the perl or write our own
replacement?

Mercifully we only use it a few times/year. Leave it to cook and do
something else for a bit (oh for a Tardis).

////////////////

Simon