Add a postbuild action for executables built with ASan on Mac OS.

build/asan.gyp

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+   'targets': [
+     {
+       'target_name': 'asan_dynamic_runtime',
+       'type': 'none',
+
+       'direct_dependent_settings': {
+         'copies': [
+           {
+             'destination': '<(PRODUCT_DIR)',
+             'files': [
+               '/usr/bin/true',
+             ],
+           },
+         ],
+         'postbuilds': [
+           {
+             'variables': {
+               'copy_asan_runtime_dylib_path':
+                   'mac/copy_asan_runtime_dylib.sh',
+               'copy_asan_runtime_dylib_options%': [
+               ],
+             },
+             'postbuild_name': 'Copy ASan runtime dylib',
+               'action': [
+                 '<(copy_asan_runtime_dylib_path)',
+                 '>@(copy_asan_runtime_dylib_options)',
+             ],
+         }],
+       },
+     },
+   ],
+}