Run "pub run" against the .packages file.

lib/src/executable.dart

 // Copyright (c) 2014, 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.
 
 library pub.executable;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
@@ skipping 102 matching lines @@
   // If we're running an executable directly from the filesystem, make sure that
   // it knows where to load the packages. If it's a dependency's executable, for
   // example, it may not have the right packages directory itself.
   if (executableUrl.scheme == 'file' || executableUrl.scheme == '') {
     // TODO(nweiz): use a .packages file once sdk#23369 is fixed.
 
     // We use an absolute path here not because the VM insists but because it's
     // helpful for the subprocess to be able to spawn Dart with
     // Platform.executableArguments and have that work regardless of the working
     // directory.
-    vmArgs.add('--package-root=${p.toUri(p.absolute(entrypoint.packagesDir))}');
+    vmArgs.add('--packages=${p.toUri(p.absolute(entrypoint.packagesFile))}');
   }
 
   vmArgs.add(executableUrl.toString());
   vmArgs.addAll(args);
 
   var process = await Process.start(Platform.executable, vmArgs);
 
   _forwardSignals(process);
 
   // Note: we're not using process.std___.pipe(std___) here because
@@ skipping 133 matching lines @@
 }
 
 /// Runs the executable snapshot at [snapshotPath].
 Future<int> _runCachedExecutable(Entrypoint entrypoint, String snapshotPath,
     List<String> args) {
   return runSnapshot(snapshotPath, args, checked: true, recompile: () {
     log.fine("Precompiled executable is out of date.");
     return entrypoint.precompileExecutables();
   });
 }