Fail ios workflow when simctl does not work (#15628) * fail ios workflow when simctl does not work * missed rename commit * address comments

diff --git a/packages/flutter_tools/lib/src/ios/ios_workflow.dart b/packages/flutter_tools/lib/src/ios/ios_workflow.dart
index 55b5ed3..d561ff0 100644
--- a/packages/flutter_tools/lib/src/ios/ios_workflow.dart
+++ b/packages/flutter_tools/lib/src/ios/ios_workflow.dart

@@ -23,7 +23,7 @@
 
   // We need xcode (+simctl) to list simulator devices, and libimobiledevice to list real devices.
   @override
-  bool get canListDevices => xcode.isInstalledAndMeetsVersionCheck;
+  bool get canListDevices => xcode.isInstalledAndMeetsVersionCheck && xcode.isSimctlInstalled;
 
   // We need xcode to launch simulator devices, and ideviceinstaller and ios-deploy
   // for real devices.
@@ -87,6 +87,13 @@
           'Xcode end user license agreement not signed; open Xcode or run the command \'sudo xcodebuild -license\'.'
         ));
       }
+      if (!xcode.isSimctlInstalled) {
+        xcodeStatus = ValidationType.partial;
+        messages.add(new ValidationMessage.error(
+          'Xcode requires additional components to be installed in order to run.\n'
+          'Launch Xcode and install additional required components when prompted.'
+        ));
+      }
       if ((await macDevMode).contains('disabled')) {
         xcodeStatus = ValidationType.partial;
         messages.add(new ValidationMessage.error(

diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index 29bf8c8..aff5667 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart

@@ -149,6 +149,23 @@
     return _eulaSigned;
   }
 
+  bool _isSimctlInstalled;
+
+  /// Verifies that simctl is installed by trying to run it.
+  bool get isSimctlInstalled {
+    if (_isSimctlInstalled == null) {
+      try {
+        // This command will error if additional components need to be installed in
+        // xcode 9.2 and above.
+        final ProcessResult result = processManager.runSync(<String>['/usr/bin/xcrun', 'simctl', 'list']);
+        _isSimctlInstalled = result.stderr == null;
+      } on ProcessException {
+        _isSimctlInstalled = false;
+      }
+    }
+    return _isSimctlInstalled;
+  }
+
   bool get isVersionSatisfactory {
     if (!xcodeProjectInterpreter.isInstalled)
       return false;