chore: cleanup + update nix flake

nix/derivation.nix

@@ -7,47 +7,35 @@
   SystemConfiguration,
   version,
   optimizeSize ? false,
-}: let
-  filter = path: type: let
-    path' = toString path;
-    base = baseNameOf path';
-    parent = baseNameOf (dirOf path');
+}:
+naersk.buildPackage {
+  pname = "refraction";
+  inherit version;
 
-    dirBlocklist = ["nix"];
-
-    matches = lib.any (suffix: lib.hasSuffix suffix base) [".rs"];
-    isCargo = base == "Cargo.lock" || base == "Cargo.toml";
-    isTag = parent == "tags";
-    isAllowedDir = !(builtins.elem base dirBlocklist);
-  in
-    (type == "directory" && isAllowedDir) || matches || isCargo || isTag;
-
-  filterSource = src:
-    lib.cleanSourceWith {
-      src = lib.cleanSource src;
-      inherit filter;
-    };
-in
-  naersk.buildPackage {
-    pname = "refraction";
-    inherit version;
-
-    src = filterSource ../.;
-
-    buildInputs = lib.optionals stdenv.hostPlatform.isDarwin [
-      CoreFoundation
-      Security
-      SystemConfiguration
+  src = lib.fileset.toSource {
+    root = ../.;
+    fileset = lib.fileset.unions [
+      ../src
+      ../build.rs
+      ../Cargo.lock
+      ../Cargo.toml
+      ../tags
     ];
+  };
 
-    RUSTFLAGS = lib.optionalString optimizeSize "-C codegen-units=1 -C strip=symbols -C opt-level=z";
+  buildInputs = lib.optionals stdenv.hostPlatform.isDarwin [
+    CoreFoundation
+    Security
+    SystemConfiguration
+  ];
 
-    meta = with lib; {
-      mainProgram = "refraction";
-      description = "Discord bot for Prism Launcher";
-      homepage = "https://github.com/PrismLauncher/refraction";
-      license = licenses.gpl3Plus;
-      platforms = with platforms; linux ++ darwin;
-      maintainers = with maintainers; [getchoo Scrumplex];
-    };
-  }
+  cargoBuildFlags = lib.optionals optimizeSize ["-C" "codegen-units=1" "-C" "strip=symbols" "-C" "opt-level=z"];
+
+  meta = with lib; {
+    mainProgram = "refraction";
+    description = "Discord bot for Prism Launcher";
+    homepage = "https://github.com/PrismLauncher/refraction";
+    license = licenses.gpl3Plus;
+    maintainers = with maintainers; [getchoo Scrumplex];
+  };
+}