Use the provided dart sdk path in worker mode

pkg/analyzer_cli/test/build_mode_test.dart

Index: pkg/analyzer_cli/test/build_mode_test.dart
diff --git a/pkg/analyzer_cli/test/build_mode_test.dart b/pkg/analyzer_cli/test/build_mode_test.dart
index dcc242321a4a0aa798dc9b3cf598978acc45ef9d..831a45ea70669d2dd192077beb839e63de8e9244 100644
--- a/pkg/analyzer_cli/test/build_mode_test.dart
+++ b/pkg/analyzer_cli/test/build_mode_test.dart
@@ -74,7 +74,7 @@ class WorkerLoopTest {
     expect(connection.outputList, hasLength(1));
 
     var response = connection.outputList[0];
-    expect(response.exitCode, WorkerLoop.EXIT_CODE_OK);
+    expect(response.exitCode, WorkerLoop.EXIT_CODE_OK, reason: response.output);
     expect(
         response.output,
         allOf(contains('errorSink a'), contains('errorSink a'),