nix: init tooling

flake.nix

@@ -0,0 +1,21 @@
+{
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
+
+  outputs = {
+    self,
+    nixpkgs,
+  }: let
+    systems = ["x86_64-linux"];
+    forEachSystem = nixpkgs.lib.genAttrs systems;
+    pkgsForEach = nixpkgs.legacyPackages;
+  in {
+    packages = forEachSystem (system: {
+      eris = pkgsForEach.${system}.callPackage ./nix/package.nix {};
+      default = self.packages.${system}.eris;
+    });
+
+    devShells = forEachSystem (system: {
+      default = pkgsForEach.${system}.callPackage ./nix/shell.nix {};
+    });
+  };
+}