third_party: Add the libsync library from Android

third_party/libsync/BUILD.gn

+# Copyright 2016 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.
+
+config("libsync_config") {
+  include_dirs = [ "include" ]
+}
+
+source_set("libsync") {
+  sources = [
+    "include/linux/sw_sync.h",
+    "include/linux/sync.h",
+    "include/sw_sync.h",
+    "include/sync/sync.h",
+    "sync.c",
+  ]
+
+  # TODO(reveman): Remove this when crbug.com/591791 has been fixed.
+  defines += [ "strlcpy=strncpy" ]

[Nico, 2016/03/04 20:52:04]

ugh :-(

strlcpy and strncpy have pretty different semantics. can you add a local file
that just implements strlcpy for this project? how hard would it be to change
upstream?

which platform is this needed for? 

[reveman, 2016/03/07 17:18:25]

Done. Added the OpenBSD version of strlcpy.
Add strlcpy to glibc or change Android? glibc change was proposed 15 years ago
and is still a hot topic so I wouldn't count on that [1]. Android has wide usage
of strlcpy through the AOSP code so it seems inappropriate to start changing
that.

[1] https://lwn.net/Articles/612244/
ChromeOS.

+
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [ "//build/config/compiler:no_chromium_code" ]
+
+  public_configs = [ ":libsync_config" ]
+}