feat(ci/cd): Set up Hydra

.hydra/jobsets.nix

@@ -0,0 +1,23 @@
+let
+  pkgs = import <nixpkgs> {};
+
+  jobs = rec {
+    tarball =
+      pkgs.releaseTools.sourceTarball {
+        name = "hello-tarball";
+        src = <hello>;
+        buildInputs = (with pkgs; [ gettext texLive texinfo ]);
+      };
+
+    build =
+      { system ? builtins.currentSystem }:
+
+      let pkgs = import <nixpkgs> { inherit system; }; in
+      pkgs.releaseTools.nixBuild {
+        name = "hello";
+        src = jobs.tarball;
+        configureFlags = [ "--disable-silent-rules" ];
+      };
+  };
+in
+  jobs

.hydra/spec.json

@@ -0,0 +1,22 @@
+{
+  "nixpkgs": {
+    "enabled": 1,
+    "hidden": false,
+    "description": "Nixpkgs",
+    "nixexprinput": "nixpkgs",
+    "nixexprpath": "pkgs/top-level/release.nix",
+    "checkinterval": 300,
+    "schedulingshares": 100,
+    "enableemail": false,
+    "enable_dynamic_run_command": false,
+    "emailoverride": "",
+    "keepnr": 3,
+    "inputs": {
+      "nixpkgs": {
+          "type": "git",
+          "value": "git://github.com/NixOS/nixpkgs.git master",
+          "emailresponsible": false
+      }
+    }
+  }
+}