flake-info: use saner nix packaging method

When trying to first work in this I naive approached it with
`nix-shell`. That of course lead to the fixed output bollocks failing
with a hash mismatch. By making use of the `cargoLock` attribute on
`buildRustPackage` we can tame the FOD-beast and only have to provide
one hash manually for a single package (that we fetch from a GitHub
repository).

This also means that updating dependencies will be simpler as the native
Cargo.lock file can be used.

flake-info/default.nix

@@ -1,16 +1,17 @@
 { pkgs ? import <nixpkgs> { } }: with pkgs;
-
-
-
-
 rustPlatform.buildRustPackage rec {
-    name = "flake-info";
-    src = ./.;
-    cargoSha256 = "sha256-TA1WEvmOfnxQ+rRwkIPN1t4VPrDL6pq+WnPHVu2/CPE=";
-    nativeBuildInputs = [ pkg-config ];
-    buildInputs = [ openssl openssl.dev ] ++ lib.optional pkgs.stdenv.isDarwin [libiconv darwin.apple_sdk.frameworks.Security];
-    checkFlags = [
-        "--skip elastic::tests"
-        "--skip nix_gc::tests"
-    ];
+  name = "flake-info";
+  src = ./.;
+  cargoLock = {
+    lockFile = ./Cargo.lock;
+    outputHashes = {
+      "elasticsearch-8.0.0-alpha.1" = "0x8iw4m16vy6i28mj30aqdwfw4a3hd174l8l9yigddn3cr53cagx";
+    };
+  };
+  nativeBuildInputs = [ pkg-config ];
+  buildInputs = [ openssl openssl.dev ] ++ lib.optional pkgs.stdenv.isDarwin [ libiconv darwin.apple_sdk.frameworks.Security ];
+  checkFlags = [
+    "--skip elastic::tests"
+    "--skip nix_gc::tests"
+  ];
 }