Restructure flake.nix for static compilation (#86)

* Expose bluetui package in legacyPackages

* git ignore result directory for nix build

* Treat result as a file in gitignore

.gitignore

@@ -1,2 +1,3 @@
 /target
 .direnv/
+result

flake.nix

@@ -19,6 +19,7 @@
       system: let
         overlays = [(import rust-overlay)];
         pkgs = import nixpkgs {inherit system overlays;};
+        bluetui = pkgs.callPackage ./package.nix {};
       in {
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
@@ -28,28 +29,13 @@
             self.packages.${system}.default
           ];
         };
-        packages = rec {
+        packages = {
           default = bluetui;
-          bluetui = let
-            cargo = (pkgs.lib.importTOML ./Cargo.toml).package;
-          in
-            pkgs.rustPlatform.buildRustPackage {
-              pname = cargo.name;
-              version = cargo.version;
-              src = ./.;
-              cargoLock.lockFile = ./Cargo.lock;
-
-              buildInputs = with pkgs; [dbus];
-              nativeBuildInputs = with pkgs; [pkg-config];
-
-              meta = {
-                description = cargo.description;
-                homepage = cargo.homepage;
-                license = pkgs.lib.licenses.gpl3Only;
-                maintainers = with pkgs.lib.maintainers; [samuel-martineau];
-              };
-            };
+          inherit bluetui;
         };
+        legacyPackages = pkgs.extend(final: prev: {
+          bluetui = final.callPackage ./package.nix {};
+        });
       }
     );
 }

package.nix

@@ -0,0 +1,25 @@
+{
+  lib,
+  rustPlatform,
+  dbus,
+  pkg-config,
+}:
+let
+  cargo = lib.importTOML ./Cargo.toml;
+in
+rustPlatform.buildRustPackage {
+  pname = cargo.package.name;
+  version = cargo.package.version;
+  src = ./.;
+  cargoLock.lockFile = ./Cargo.lock;
+
+  buildInputs = [dbus];
+  nativeBuildInputs = [pkg-config];
+
+  meta = {
+    description = cargo.package.description;
+    homepage = cargo.package.homepage;
+    license = lib.licenses.gpl3Only;
+    maintainers = with lib.maintainers; [samuel-martineau];
+  };
+}