Find sdk path with cli_util (#2567)

diff --git a/lib/src/dart.dart b/lib/src/dart.dart
index 93a06d0..5b40579 100644
--- a/lib/src/dart.dart
+++ b/lib/src/dart.dart
@@ -14,6 +14,7 @@
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/error/error.dart';
+import 'package:cli_util/cli_util.dart';
 import 'package:path/path.dart' as p;
 
 import 'exceptions.dart';
@@ -112,7 +113,8 @@
       }
 
       var contextBuilder = ContextBuilder();
-      var context = contextBuilder.createContext(contextRoot: root);
+      var context = contextBuilder.createContext(
+          contextRoot: root, sdkPath: getSdkPath());
       _contexts[contextRootPath] = context;
     }
   }
diff --git a/pubspec.yaml b/pubspec.yaml
index 546fdbe..3e94e31 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -10,6 +10,7 @@
   analyzer: ^0.39.4
   args: ^1.4.1
   async: ^2.0.0
+  cli_util: ^0.2.0
   collection: ^1.8.0
   crypto: ^2.0.0
   http: ^0.12.0