Use simctl exit code instead of stderr (#73070)

packages/flutter_tools/lib/src/macos/xcode.dart

@@ -124,7 +124,7 @@ class Xcode {
         final RunResult result = _processUtils.runSync(
           <String>[...xcrunCommand(), 'simctl', 'list'],
         );
-        _isSimctlInstalled = result.stderr == null || result.stderr == '';
+        _isSimctlInstalled = result.exitCode == 0;
       } on ProcessException {
         _isSimctlInstalled = false;
       }

packages/flutter_tools/test/general.shard/macos/xcode_test.dart

@@ -140,6 +140,53 @@ void main() {
         expect(xcode.isInstalledAndMeetsVersionCheck, isFalse);
       });
 
+      testWithoutContext('isSimctlInstalled is true when simctl list succeeds', () {
+        when(mockXcodeProjectInterpreter.xcrunCommand()).thenReturn(<String>['xcrun']);
+        fakeProcessManager.addCommand(
+          const FakeCommand(
+            command: <String>[
+              'xcrun',
+              'simctl',
+              'list',
+            ],
+          ),
+        );
+        final Xcode xcode = Xcode(
+          logger: logger,
+          platform: FakePlatform(operatingSystem: 'macos'),
+          fileSystem: MemoryFileSystem.test(),
+          processManager: fakeProcessManager,
+          xcodeProjectInterpreter: mockXcodeProjectInterpreter,
+        );
+
+        expect(xcode.isSimctlInstalled, isTrue);
+        expect(fakeProcessManager.hasRemainingExpectations, isFalse);
+      });
+
+      testWithoutContext('isSimctlInstalled is true when simctl list fails', () {
+        when(mockXcodeProjectInterpreter.xcrunCommand()).thenReturn(<String>['xcrun']);
+        fakeProcessManager.addCommand(
+          const FakeCommand(
+            command: <String>[
+              'xcrun',
+              'simctl',
+              'list',
+            ],
+            exitCode: 1,
+          ),
+        );
+        final Xcode xcode = Xcode(
+          logger: logger,
+          platform: FakePlatform(operatingSystem: 'macos'),
+          fileSystem: MemoryFileSystem.test(),
+          processManager: fakeProcessManager,
+          xcodeProjectInterpreter: mockXcodeProjectInterpreter,
+        );
+
+        expect(xcode.isSimctlInstalled, isFalse);
+        expect(fakeProcessManager.hasRemainingExpectations, isFalse);
+      });
+
       group('macOS', () {
         Xcode xcode;
         FakePlatform platform;

packages/flutter_tools/test/general.shard/macos/xcode_validator_test.dart

@@ -7,12 +7,9 @@ import 'package:flutter_tools/src/doctor.dart';
 import 'package:flutter_tools/src/macos/xcode.dart';
 import 'package:flutter_tools/src/macos/xcode_validator.dart';
 import 'package:mockito/mockito.dart';
-import 'package:process/process.dart';
 
 import '../../src/common.dart';
-import '../../src/context.dart';
 
-class MockProcessManager extends Mock implements ProcessManager {}
 class MockXcode extends Mock implements Xcode {}
 
 void main() {