add gn rules for rust build changes

Change-Id: I90689872dd6dc4e79a10f565bc05b8d378f92ea9
diff --git a/BUILD.gn b/BUILD.gn
new file mode 100644
index 0000000..977b1c7
--- /dev/null
+++ b/BUILD.gn
@@ -0,0 +1,23 @@
+# Copyright 2018 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.
+
+# This file is currently a stopgap for building on Fuchsia
+# contact bwb@google.com if you are running into problems with
+# how it is mirrored
+
+import("//build/rust/rustc_library.gni")
+
+rustc_library("rustyline") {
+  name = "rustyline"
+  deps = [
+    "//garnet/public/rust/crates/fuchsia-device",
+    "//garnet/public/rust/crates/fuchsia-zircon:fuchsia-zircon-rustc",
+
+    "//third_party/rust-crates/rustc_deps:log",
+    "//third_party/rust-crates/rustc_deps:libc",
+    "//third_party/rust-crates/rustc_deps:unicode-segmentation",
+    "//third_party/rust-crates/rustc_deps:unicode-width",
+    "//third_party/rust-crates/rustc_deps:encode_unicode",
+  ]
+}