Process tests work across platforms.

tests/standalone/src/ProcessTestUtil.dart

+// Copyright (c) 2011, 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.
+
+String getProcessTestFileName() {
+  var names = ['out/Release_ia32/process_test',
+               'out/Debug_ia32/process_test',
+               'xcodebuild/Release_ia32/process_test',
+               'xcodebuild/Debug_ia32/process_test',
+               'Release_ia32/process_test.exe',
+               'Debug_ia32/process_test.exe'];
+  for (var name in names) {
+    if (new File(name).existsSync()) {
+      return name;
+    }
+  }
+  Expect.fail('Could not find the process_test program.');
+}