title: Flutter cannot be apgraded anymore
body: <p>After downloading the flutter archive and installing on macbook, everything works fine, but once I typed the <code>flutter upgrade</code> command the process failed and I got the error below.</p>
  <pre><code>Unhandled exception:
  Invalid argument(s): Cannot find executable for sysctl.
  #0      _getExecutable (package:process/src/interface/local_process_manager.dart:124:5)
  #1      LocalProcessManager.runSync (package:process/src/interface/local_process_manager.dart:91:30)
  #2      ErrorHandlingProcessManager.runSync.&lt;anonymous closure&gt; (package:flutter_tools/src/base/error_handling_io.dart:649:37)
  #3      _runSync (package:flutter_tools/src/base/error_handling_io.dart:548:14)
  #4      ErrorHandlingProcessManager.runSync (package:flutter_tools/src/base/error_handling_io.dart:649:12)
  #5      _DefaultProcessUtils.runSync (package:flutter_tools/src/base/process.dart:420:51)
  #6      _MacOSUtils.hostPlatform (package:flutter_tools/src/base/os.dart:305:25)
  #7      _MacOSUtils.name (package:flutter_tools/src/base/os.dart:291:123)
  #8      new _DefaultUsage (package:flutter_tools/src/reporting/usage.dart:247:18)
  #9      new Usage (package:flutter_tools/src/reporting/usage.dart:81:9)
  #10     runInContext.&lt;anonymous closure&gt; (package:flutter_tools/src/context_runner.dart:263:20)
  #11     AppContext._generateIfNecessary.&lt;anonymous closure&gt; (package:flutter_tools/src/base/context.dart:104:41)
  #12     _LinkedHashMapMixin.putIfAbsent (dart:collection-patch/compact_hash.dart:291:23)
  #13     AppContext._generateIfNecessary (package:flutter_tools/src/base/context.dart:92:20)
  #14     AppContext.get (package:flutter_tools/src/base/context.dart:121:32)
  #15     flutterUsage (package:flutter_tools/src/globals.dart:55:35)
  #16     _handleToolError (package:flutter_tools/runner.dart:133:13)
  #17     run.&lt;anonymous closure&gt;.&lt;anonymous closure&gt; (package:flutter_tools/runner.dart:87:13)
  #18     run.&lt;anonymous closure&gt;.&lt;anonymous closure&gt; (package:flutter_tools/runner.dart:81:17)
  #19     _rootRunBinary (dart:async/zone.dart:1222:13)
  #20     _CustomZone.runBinary (dart:async/zone.dart:1107:19)
  #21     runZonedGuarded.&lt;anonymous closure&gt; (dart:async/zone.dart:1601:18)
  #22     _CustomZone.handleUncaughtError (dart:async/zone.dart:1076:19)
  #23     Future._propagateToListeners (dart:async/future_impl.dart:646:16)
  #24     Future._completeError (dart:async/future_impl.dart:537:5)
  #25     _completeOnAsyncError (dart:async-patch/async_patch.dart:264:13)
  #26     run.&lt;anonymous closure&gt;.&lt;anonymous closure&gt; (package:flutter_tools/runner.dart)
  &lt;asynchronous suspension&gt;
  </code></pre>
  <p><strong>Please can someone help me?</strong></p>