Specify Kotlin version as well

.cirrus.yml

@@ -307,7 +307,7 @@ task:
           CHANNEL: "stable"
       << : *BUILD_ALL_PACKAGES_APP_TEMPLATE
       create_all_packages_app_legacy_script:
-        - $PLUGIN_TOOL_COMMAND create-all-packages-app --agp-version=4.1.0 --gradle-version=6.5 --output-dir=legacy/ --android-language=java --exclude script/configs/exclude_all_packages_app.yaml
+        - $PLUGIN_TOOL_COMMAND create-all-packages-app --agp-version=4.1.0 --gradle-version=6.5 --kotlin-version=1.4.32 --output-dir=legacy/ --android-language=java --exclude script/configs/exclude_all_packages_app.yaml
       build_all_packages_legacy_script:
         - cd legacy/all_packages
         - flutter build $BUILD_ALL_ARGS --debug

script/tool/lib/src/create_all_packages_app_command.dart

@@ -50,11 +50,15 @@ class CreateAllPackagesAppCommand extends PackageCommand {
         help: 'The Gradle version to use in the created app, instead of the '
             'default `flutter create`d version. Will generally need to be used '
             ' with $_agpVersionFlag due to compatibility limits.');
+    argParser.addOption(_kotlinVersionFlag,
+        help: 'The Kotlin version to use in the created app, instead of the '
+            'default `flutter create`d version.');
   }
 
   static const String _androidLanguageFlag = 'android-language';
   static const String _agpVersionFlag = 'agp-version';
   static const String _gradleVersionFlag = 'gradle-version';
+  static const String _kotlinVersionFlag = 'kotlin-version';
   static const String _outputDirectoryFlag = 'output-dir';
 
   /// The location to create the synthesized app project.
@@ -105,7 +109,9 @@ class CreateAllPackagesAppCommand extends PackageCommand {
     }
 
     await Future.wait(<Future<void>>[
-      _updateTopLevelGradle(agpVersion: getNullableStringArg(_agpVersionFlag)),
+      _updateTopLevelGradle(
+          agpVersion: getNullableStringArg(_agpVersionFlag),
+          kotlinVersion: getNullableStringArg(_kotlinVersionFlag)),
       _updateGradleWrapper(
           gradleVersion: getNullableStringArg(_gradleVersionFlag)),
       _updateAppGradle(),
@@ -178,7 +184,10 @@ class CreateAllPackagesAppCommand extends PackageCommand {
     file.writeAsStringSync(output.toString());
   }
 
-  Future<void> _updateTopLevelGradle({String? agpVersion}) async {
+  Future<void> _updateTopLevelGradle({
+    String? agpVersion,
+    String? kotlinVersion,
+  }) async {
     final File gradleFile = app
         .platformDirectory(FlutterPlatform.android)
         .childFile('build.gradle');
@@ -189,6 +198,10 @@ class CreateAllPackagesAppCommand extends PackageCommand {
           'com.android.tools.build:': <String>[
             "        classpath 'com.android.tools.build:gradle:$agpVersion'"
           ],
+        if (kotlinVersion != null)
+          'ext.kotlin_version =': <String>[
+            "    ext.kotlin_version = '$kotlinVersion'"
+          ],
       },
     );
   }

script/tool/test/create_all_packages_app_command_test.dart

@@ -332,16 +332,18 @@ project 'Runner', {
           ]));
     });
 
-    test('Android AGP and Gradle versions are modified if requested', () async {
+    test('Android dependency versions are modified if requested', () async {
       writeFakeFlutterCreateOutput(testRoot);
       createFakePlugin('plugina', packagesDir);
 
       const String agpVersion = '9.8.7';
       const String gradleVersion = '99.87';
+      const String kotlinVersion = '7.8.9';
       await runCapturingPrint(runner, <String>[
         'create-all-packages-app',
         '--agp-version=$agpVersion',
-        '--gradle-version=$gradleVersion'
+        '--gradle-version=$gradleVersion',
+        '--kotlin-version=$kotlinVersion',
       ]);
 
       final List<String> buildGradle = command.app
@@ -357,8 +359,10 @@ project 'Runner', {
 
       expect(
           buildGradle,
-          contains(contains(
-              "classpath 'com.android.tools.build:gradle:$agpVersion'")));
+          containsAll(<Matcher>[
+            contains("ext.kotlin_version = '$kotlinVersion'"),
+            contains("classpath 'com.android.tools.build:gradle:$agpVersion'"),
+          ]));
       expect(
           gradleWrapper,
           contains(contains(