flutter: remove rec

pkgs/development/compilers/flutter/build-support/build-flutter-application.nix

···
   ++ flutterFlags;
 
   builderArgs =
-    rec {
+    let
       universal = args // {
         inherit flutterMode flutterFlags flutterBuildFlags;
 
···
           fi
         '';
       };
+    in
+    {
+      inherit universal;
 
       linux = universal // {
         outputs = universal.outputs or [ ] ++ [ "debug" ];

pkgs/development/compilers/flutter/default.nix

···
     in
     (mkCustomFlutter args).overrideAttrs (
       prev: next: {
-        passthru = next.passthru // rec {
+        passthru = next.passthru // {
           inherit wrapFlutter mkCustomFlutter mkFlutter;
           buildFlutterApplication = callPackage ./build-support/build-flutter-application.nix {
             flutter = wrapFlutter (mkCustomFlutter args);

pkgs/development/compilers/flutter/flutter-tools.nix

···
       content_hash = "1111111111111111111111111111111111111111";
     };
   };
+
+  dartEntryPoints."flutter_tools.snapshot" = "bin/flutter_tools.dart";
 in
-buildDartApplication.override { inherit dart; } rec {
+buildDartApplication.override { inherit dart; } {
   pname = "flutter-tools";
-  inherit version;
+  inherit version dartEntryPoints;
   dartOutputType = "jit-snapshot";
 
   src = flutterSrc;
-  sourceRoot = "${src.name}/packages/flutter_tools";
+  sourceRoot = "${flutterSrc.name}/packages/flutter_tools";
   postUnpack = ''chmod -R u+w "$NIX_BUILD_TOP/source"'';
 
   inherit patches;
···
     ln -s '${dart}' "$FLUTTER_ROOT/bin/cache/dart-sdk"
   '';
 
-  dartEntryPoints."flutter_tools.snapshot" = "bin/flutter_tools.dart";
   dartCompileFlags = [ "--define=NIX_FLUTTER_HOST_PLATFORM=${systemPlatform}" ];
 
   # The Dart wrapper launchers are useless for the Flutter tool - it is designed