Remove the "pkgbuild" step on the bots.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 1773 matching lines @@
     }
   }
 
   List<int> _truncatedTail() => tail.length > TAIL_LENGTH
       ? tail.sublist(tail.length - TAIL_LENGTH)
       : tail;
 
   void _checkUtf8(List<int> data) {
     try {
       UTF8.decode(data, allowMalformed: false);
-    } on FormatException catch (e) {
+    } on FormatException {
       hasNonUtf8 = true;
       String malformed = UTF8.decode(data, allowMalformed: true);
       data
         ..clear()
         ..addAll(UTF8.encode(malformed))
         ..addAll("""
 
   *****************************************************************************
 
   test.dart: The output of this test contained non-UTF8 formatted data.
@@ skipping 1436 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }