Add .gyp file for the DBus client library ebuild.

The new update_engine-client client library ebuild will use this .gyp
file to generate and install the headers.

Bug: 23084776
TEST=`emerge-link update_engine` with the new ebuild in CL:296831

Change-Id: Ifcb9f5aa223e345af18f7273c163614445e75441
diff --git a/update_engine-client.gyp b/update_engine-client.gyp
new file mode 100644
index 0000000..588fc63
--- /dev/null
+++ b/update_engine-client.gyp
@@ -0,0 +1,41 @@
+#
+# Copyright (C) 2015 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+{
+  'targets': [
+    # update_engine client library generated headers. Used by other daemons and
+    # by the update_engine_client console program to interact with
+    # update_engine.
+    {
+      'target_name': 'libupdate_engine-client-headers',
+      'type': 'none',
+      'actions': [
+        {
+          'action_name': 'update_engine_client-dbus-proxies',
+          'variables': {
+            'dbus_service_config': 'dbus_bindings/dbus-service-config.json',
+            'proxy_output_file': 'include/update_engine/dbus-proxies.h',
+            'mock_output_file': 'include/update_engine/dbus-proxy-mocks.h',
+            'proxy_path_in_mocks': 'update_engine/dbus-proxies.h',
+          },
+          'sources': [
+            'dbus_bindings/org.chromium.UpdateEngineInterface.dbus-xml',
+          ],
+          'includes': ['../../../platform2/common-mk/generate-dbus-proxies.gypi'],
+        },
+      ],
+    },
+  ],
+}