chore(workspace): add nix stuff

.gitignore

@@ -1,3 +1,4 @@
 .build/
+result
 *.xcodeproj
-Package.resolved
+Package.resolved

default.nix

@@ -0,0 +1,22 @@
+{ lib, swift, swiftpm, swiftpm2nix }:
+
+with lib.sources;
+
+let
+  generated = swiftpm2nix.helpers ./nix;
+in
+
+swift.stdenv.mkDerivation rec {
+  pname = "nanoseconds";
+  version = "1.1.3";
+  src = cleanSource ./.;
+  nativeBuildInputs = [ swift swiftpm ];
+
+  configurePhase = generated.configure;
+
+  installPhase = ''
+    binPath="$(swiftpmBinPath)"
+    mkdir -p $out/lib
+    cp -r $binPath/* $out/lib
+  '';
+}

flake.nix

@@ -0,0 +1,25 @@
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  outputs =
+    { self
+    , nixpkgs
+    , flake-utils
+    ,
+    }:
+
+      with flake-utils.lib;
+
+      eachDefaultSystem (system:
+
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+
+      {
+        formatter = pkgs.nixpkgs-fmt;
+        packages.default = pkgs.callPackage ./default.nix { };
+        devShells.default = pkgs.callPackage ./shell.nix { };
+      });
+}

nix/default.nix

@@ -0,0 +1,5 @@
+# This file was generated by swiftpm2nix.
+{
+  workspaceStateFile = ./workspace-state.json;
+  hashes = { };
+}

nix/workspace-state.json

@@ -0,0 +1,7 @@
+{
+  "object": {
+    "artifacts": [],
+    "dependencies": []
+  },
+  "version": 6
+}

shell.nix

@@ -0,0 +1,12 @@
+{ pkgs, swift }:
+
+pkgs.mkShell.override { inherit (swift) stdenv; }
+
+{
+  buildInputs = with pkgs; [
+    swift
+    swiftPackages.Foundation
+    swiftpm
+    swiftpm2nix
+  ];
+}