Implements support for Nix's new Perl bindings[1]. The current state
basically does `openStore()`, but always uses `auto` and doesn't support
stores at other URIs.
Even though the stores are cached inside the Perl implementation, I
decided to instantiate those once in the Nix helper module. That way
store openings aren't cluttered across the entire codebase. Also, there
are two stores used later on - MACHINE_LOCAL_STORE for `auto`,
BINARY_CACHE_STORE for the one from `store_uri` in `hydra.conf` - and
using consistent names should make the intent clearer then.
This doesn't contain any behavioral changes, i.e. the build product
availability issue from #1352 isn't fixed. This patch only contains the
migration to the new API.
[1] https://github.com/NixOS/nix/pull/9863
This requires adding the following to hydra.conf:
binary_cache_key_name = <key-name>
binary_cache_private_key_file = <path-to-private-key>
e.g.
binary_cache_key_name = hydra.nixos.org-1
binary_cache_private_key_file = /home/hydra/cache-key.sec
