ref(nix): split package to default.nix

default.nix

@@ -0,0 +1,42 @@
+{
+  lib,
+  stdenv,
+  rust-bin, # From overlay
+  makeRustPlatform,
+  packageToml,
+  rust,
+  libiconv,
+  darwin,
+  python3,
+}: let
+  testDeps = [
+    python3
+  ];
+
+  buildDeps = rust:
+    [
+      rust
+    ]
+    ++ (lib.optionals stdenv.isDarwin [
+      libiconv
+      darwin.apple_sdk.frameworks.Foundation
+    ])
+    ++ testDeps;
+
+  mkPackage = rust:
+    (makeRustPlatform {
+      cargo = rust;
+      rustc = rust;
+    })
+    .buildRustPackage {
+      pname = packageToml.name;
+      inherit (packageToml) version;
+      src = builtins.path {
+        path = ./.;
+        inherit (packageToml) name;
+      };
+      cargoLock.lockFile = ./Cargo.lock;
+      buildInputs = buildDeps rust;
+      dontUseCargoParallelTests = true;
+    };
+in (mkPackage rust-bin.stable.latest.minimal)