fix: windows flutter.bat compatibility for update command

packages/flutterfire_cli/lib/src/commands/update.dart

@@ -76,28 +76,29 @@ class UpdateCommand extends FlutterFireCommand {
     commandRequiresFlutterApp();
 
     logger.stdout('Cleaning up current workspace ...');
+    final flutterCmd = Platform.isWindows ? 'flutter.bat' : 'flutter';
     await Process.run(
-      'flutter',
+      flutterCmd,
       ['clean'],
     );
-    await Process.run(
-      'rm',
-      ['pubspec.lock'],
-    );
+    final pubspecLockFile = File('pubspec.lock');
+    if (pubspecLockFile.existsSync()) {
+      await pubspecLockFile.delete();
+    }
 
     logger.stdout('Upgrading all firebase plugins to the latest version ...');
     for (final package in flutterfirePackages) {
       // We run each package individually because chaining them
       // will fail at the first package not in the pubspec.
       await Process.run(
-        'flutter',
+        flutterCmd,
         ['pub', 'upgrade', '--major-versions', package],
       );
     }
 
     logger.stdout("Running 'flutter pub get'...");
     await Process.run(
-      'flutter',
+      flutterCmd,
       ['pub', 'get'],
     );
 

packages/flutterfire_cli/lib/src/firebase/firebase_dart_configuration_write.dart

@@ -177,14 +177,14 @@ class FirebaseDartConfigurationWrite {
       }
     }
 
-    return formatList(fileConfigurationLines).join('\n');
+    return '${formatList(fileConfigurationLines).join('\n')}\n';
   }
 
   String _buildConfigurationFile() {
     _stringBuffer.clear();
     _writeHeader();
     _writeClass();
-    return formatList(_stringBuffer.toString().split('\n')).join('\n');
+    return '${formatList(_stringBuffer.toString().split('\n')).join('\n')}\n';
   }
 
   // ensure only one empty line between each static property