fix windows codegen (#29062)

packages/flutter_tools/lib/src/codegen.dart

diff --git a/packages/flutter_tools/lib/src/codegen.dart b/packages/flutter_tools/lib/src/codegen.dart
index 3e94298..d53714a 100644
--- a/packages/flutter_tools/lib/src/codegen.dart
+++ b/packages/flutter_tools/lib/src/codegen.dart
@@ -149,7 +149,7 @@
       depFilePath: depFilePath,
       targetModel: targetModel,
       // Pass an invalid file name to prevent frontend_server from initializing from dill.
-      initializeFromDill: ' ',
+      initializeFromDill: 'none_file',
     );
   }
 }
@@ -189,7 +189,7 @@
       targetModel: TargetModel.flutter,
       unsafePackageSerialization: unsafePackageSerialization,
       // Pass an invalid file name to prevent frontend_server from initializing from dill.
-      initializeFromDill: ' ',
+      initializeFromDill: 'none_file',
     );
     return CodeGeneratingResidentCompiler._(residentCompiler, codegenDaemon);
   }