Defer to engine for option-aware context config.

lib/src/options.dart

Index: lib/src/options.dart
diff --git a/lib/src/options.dart b/lib/src/options.dart
index ac1463ba491369ce2098dac54e1e4d10972544a3..966090e036bcf82c422c6f68e5a2e8816a9a5f5f 100644
--- a/lib/src/options.dart
+++ b/lib/src/options.dart
@@ -6,6 +6,7 @@ library analyzer_cli.src.options;
 
 import 'dart:io';
 
+import 'package:analyzer_cli/src/driver.dart';
 import 'package:args/args.dart';
 import 'package:cli_util/cli_util.dart' show getSdkDir;
 
@@ -18,7 +19,7 @@ ExitHandler exitHandler = exit;
 
 /// Print the given message to stderr and exit with the given [exitCode]
 void printAndFail(String message, {int exitCode: 15}) {
-  stderr.writeln(message);
+  errorSink.writeln(message);
   exitHandler(exitCode);
 }