Add GN files for bspatch.

third_party/bspatch/BUILD.gn

Index: third_party/bspatch/BUILD.gn
diff --git a/third_party/bspatch/BUILD.gn b/third_party/bspatch/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..39296159f8363a450d851a4ec824feb32038e963
--- /dev/null
+++ b/third_party/bspatch/BUILD.gn
@@ -0,0 +1,17 @@
+# Copyright 2015 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.
+
+source_set("bspatch") {
+  sources = [
+    "mbspatch.cc",
+    "mbspatch.h",
+  ]
+
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [ "//build/config/compiler:no_chromium_code" ]
+
+  deps = [
+    "//third_party/lzma_sdk",
+  ]
+}