Move the cyberpunk build script into the cyberpunk directory

cyberpunk-splash/default.nix

@@ -0,0 +1,36 @@
+{ pkgs, typeshare }:
+let
+  standardOverride = attrs: {
+      nativeBuildInputs = [
+        pkgs.pkg-config
+        pkgs.gtk4
+      ];
+      buildInputs = [
+        typeshare
+      ];
+      verbose = true;
+  };
+  customBuildInfo = pkgs: pkgs.buildRustCrate.override {
+    defaultCrateOverrides = pkgs.defaultCrateOverrides // {
+      cairo-sys-rs = standardOverride;
+      graphene-sys = standardOverride;
+      gobject-sys = standardOverride;
+      pango-sys = standardOverride;
+      gio-sys = standardOverride;
+      gdk-pixbuf-sys = standardOverride;
+      gdk4-sys = standardOverride;
+      gsk4-sys = standardOverride;
+      gtk4-sys = standardOverride;
+      kifu-gtk = attrs: {
+        nativeBuildInputs = [
+          pkgs.glib
+          typeshare
+        ];
+      };
+    };
+  };
+in (import ./Cargo.nix {
+  inherit pkgs;
+  buildRustCrateForPkgs = customBuildInfo;
+  release = true;
+}).rootCrate.build

flake.nix

@@ -105,11 +105,10 @@
             kifu-wasm = import ./kifu { inherit (pkgs) rustPlatform wasm-pack; mkDerivation = pkgs.stdenv.mkDerivation; typeshare = typeshare.packages."x86_64-linux".default; };
             */
 
-            cyberpunk-splash = (import ./cyberpunk-splash/Cargo.nix {
+            cyberpunk-splash = import ./cyberpunk-splash {
               inherit pkgs;
-              buildRustCrateForPkgs = customBuildInfo;
-              release = true;
-            }).rootCrate.build;
+              typeshare = typeshare.packages."x86_64-linux".default;
+            };
           };
     };
 }