Wrap dart:convert to track utf8 decode failures (#26650)

diff --git a/packages/flutter_tools/lib/src/version.dart b/packages/flutter_tools/lib/src/version.dart
index 9e3cb56..29dbc5e 100644
--- a/packages/flutter_tools/lib/src/version.dart
+++ b/packages/flutter_tools/lib/src/version.dart
@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:convert';
 
 import 'package:meta/meta.dart';
 
@@ -15,6 +14,7 @@
 import 'base/process_manager.dart';
 import 'base/time.dart';
 import 'cache.dart';
+import 'convert.dart';
 import 'globals.dart';
 
 class FlutterVersion {