[bug#63893] gnu: nix: Update to 2.16.1

[jgart]

Hi Trofi,

I saw that you've done a fare amount of work on guix/nix packaging in 
nix-guix-gentoo and could use your expertise in this area for reviewing this 
patch set:

https://github.com/trofi/nix-guix-gentoo

If you find the time, would you be able to help review this patch series? It 
would be much appreciated.

Feel free to send a v4 patch and add yourself as co-author if you'd like to 
help directly.

Also, feel free to ignore if you don't have the time to review this one or help 
out on it.

I could particular use some guidance on enabling the tests for rapidcheck. My 
cmake knowledge is very fresh.

all best,

jgart

https://whereis.みんな/