[flutter_tools] Add documentation to "cmdline-tools component is missing"...

[flutter_tools] Add documentation to "cmdline-tools component is missing" doctor validation error (#83356)

packages/flutter_tools/lib/src/android/android_workflow.dart

@@ -186,7 +186,7 @@ class AndroidValidator extends DoctorValidator {
       return ValidationResult(ValidationType.missing, messages);
     }
     if (!androidSdk.cmdlineToolsAvailable) {
-      messages.add(const ValidationMessage.error('cmdline-tools component is missing'));
+      messages.add(ValidationMessage.error(_userMessages.androidMissingCmdTools));
       return ValidationResult(ValidationType.missing, messages);
     }
 

packages/flutter_tools/lib/src/base/user_messages.dart

@@ -120,6 +120,9 @@ class UserMessages {
   String androidSdkBuildToolsOutdated(String managerPath, int sdkMinVersion, String buildToolsMinVersion, Platform platform) =>
       'Flutter requires Android SDK $sdkMinVersion and the Android BuildTools $buildToolsMinVersion\n'
       'To update the Android SDK visit ${_androidSdkInstallUrl(platform)} for detailed instructions.';
+  String get androidMissingCmdTools => 'cmdline-tools component is missing\n'
+      'Run `path/to/sdkmanager --install "cmdline-tools;latest"`\n'
+      'See https://developer.android.com/studio/command-line for more details.';
 
   // Messages used in AndroidStudioValidator
   String androidStudioVersion(String version) => 'version $version';

packages/flutter_tools/test/general.shard/android/android_workflow_test.dart

@@ -395,11 +395,13 @@ Review licenses that have not been accepted (y/N)?
       userMessages: UserMessages(),
     );
 
+    final String errorMessage = UserMessages().androidMissingCmdTools;
+
     final ValidationResult validationResult = await androidValidator.validate();
     expect(validationResult.type, ValidationType.missing);
     expect(
       validationResult.messages.last.message,
-      'cmdline-tools component is missing',
+      errorMessage,
     );
   });