[nlio] Add GN support to include nlio headers

Change-Id: I0d84c3a8c39f8b2ca7955bb00318bafec0f12600
diff --git a/BUILD.gn b/BUILD.gn
new file mode 100644
index 0000000..a498643
--- /dev/null
+++ b/BUILD.gn
@@ -0,0 +1,29 @@
+# Copyright 2020 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+source_set("nlio") {
+  public = [
+    "include/nlbyteorder-big.h",
+    "include/nlbyteorder.h",
+    "include/nlbyteorder.hpp",
+    "include/nlbyteorder-little.h",
+    "include/nlio-base.h",
+    "include/nlio-base.hpp",
+    "include/nlio-byteorder-big.h",
+    "include/nlio-byteorder-big.hpp",
+    "include/nlio-byteorder.h",
+    "include/nlio-byteorder.hpp",
+    "include/nlio-byteorder-little.h",
+    "include/nlio-byteorder-little.hpp",
+    "include/nlio-config.h.in",
+    "include/nlio.h",
+    "include/nlio.hpp",
+    "include/nlio-private.h",
+  ]
+  public_configs = [ ":nlio_config" ]
+}
+
+config("nlio_config") {
+  include_dirs = [ "include" ]
+}