Nix daemon installation breaks cache

[dsalaza4]

When using a daemon installation of Nix, which, by the way, is the recommended one now, custom caches are not being used due to lack of trust.

For example, try running m github:fluidattacks/makes-example@main /api/env with a daemon installation,

You will get the following warning:

warning: ignoring untrusted substituter 'https://makes.cachix.org'

I think this is because trusted-substituers can only be changed by trusted-users.

I did a quick test by passing trusted-substituers and trusted-users to the nix-build command on the CLI but it did not work.

Let's investigate a comfortable way of handling this.

[dsalaza4]

@jpverde It could be a good idea to add this exception to the cache builtin in the meantime just like we do with builtins that are only supported on Linux.

[dsalaza4]

This will be addressed in #989