Init flake and make project buildable

flake.nix

@@ -0,0 +1,34 @@
+{
+  inputs = {
+    dream2nix.url = "github:nix-community/dream2nix";
+    nixpkgs.follows = "dream2nix/nixpkgs";
+  };
+
+  outputs = {
+    self,
+    dream2nix,
+    nixpkgs,
+  }: let
+    eachSystem = nixpkgs.lib.genAttrs [
+      "aarch64-darwin"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "x86_64-linux"
+    ];
+  in {
+    packages = eachSystem (system: rec {
+      hcpy = default;
+      default = dream2nix.lib.evalModules {
+        packageSets.nixpkgs = nixpkgs.legacyPackages.${system};
+        modules = [
+          ./package.nix
+          {
+            paths.projectRootFile = "flake.nix";
+            paths.projectRoot = ./.;
+            paths.package = ./.;
+          }
+        ];
+      };
+    });
+  };
+}