add cachix for ci build

[dzmitry-lahoda]

composable can donate key https://app.cachix.org/organization/composablefi/cache/polkadot#pull - as long as composalbe exists, we will pay for cache

use

https://determinate.systems/posts/magic-nix-cache for builds

or

https://github.com/nixbuild/

for builds

so builds are fast and cached

[andresilva]

Thanks for the cache key donation. I guess I can use my own cache for the initial setup (also since this is a public cache the free tier should be enough). I'll look into the links you provided.

Also I'm sorry I'm replying slowly to your issues, this is just a hobby project for me and not my main focus, so my time here is a bit more limited.

[dzmitry-lahoda]

Also I'm sorry I'm replying slowly to your issues, this is just a hobby project for me and not my main focus, so my time here is a bit more limited.

no worries. so you may consider "donate" repo to some org, like nix-community, paritytech if they accept it. i guess it will ease repo discovery and trust into it, so more PRs will follow. private repo have tendency to die more easily than org.

in case if repo donated to ComposableFi/polkadot.nix, I will be able to spend more time PRing. I need faster turnaround so, so most of things go to ComposableFe/composable repo.