Add nacl_sdk gyp meta-target.

src/untrusted/valgrind/valgrind.gyp

+# Copyright (c) 2012 The Native Client Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'includes': [
+    '../../../build/common.gypi',
+  ],
+  'targets' : [
+    {
+      'target_name': 'valgrind_lib',
+      'type': 'none',
+      'variables': {
+        'nlib_target': 'libvalgrind.a',
+        'nso_target': 'libvalgrind.so',
+        'build_glibc': 1,
+        'build_newlib': 1,
+      },
+      'sources': [
+        'valgrind_interceptors.c',
+      ],
+    },
+    {
+      'target_name': 'dynamic_annotations_lib',
+      'type': 'none',
+      'variables': {
+        'nlib_target': 'libdynamic_annotations.a',
+        'nso_target': 'libdynamic_annotations.so',
+        'build_glibc': 1,
+        'build_newlib': 0,
+      },
+      'sources': [
+        'dynamic_annotations.c',
+      ],
+    }
+  ],
+}