Add a snapshot of flutter/engine/src/build to our sdk

build/linux/unbundle/libevent.gyp

Index: build/linux/unbundle/libevent.gyp
diff --git a/build/linux/unbundle/libevent.gyp b/build/linux/unbundle/libevent.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..99d743533f6104c78d5106fa445f642f5eda2514
--- /dev/null
+++ b/build/linux/unbundle/libevent.gyp
@@ -0,0 +1,27 @@
+# Copyright 2013 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': 'libevent',
+      'type': 'none',
+      'toolsets': ['host', 'target'],
+      'variables': {
+        'headers_root_path': '.',
+        'header_filenames': [
+          'event.h',
+        ],
+      },
+      'includes': [
+        '../../build/shim_headers.gypi',
+      ],
+      'link_settings': {
+        'libraries': [
+          '-levent',
+        ],
+      },
+    }
+  ],
+}