unbundle: add GN files for flac, harfbuzz-ng, and libwebp

build/linux/unbundle/harfbuzz-ng.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.
+
+import("//build/config/linux/pkg_config.gni")
+import("//build/shim_headers.gni")
+
+pkg_config("system_harfbuzz") {
+  packages = [
+    "harfbuzz",
+    "harfbuzz-icu",
+  ]
+}
+
+shim_headers("harfbuzz_shim") {
+  root_path = "src"
+  headers = [ "hb.h" ]
+}
+
+source_set("harfbuzz-ng") {
+  deps = [
+    ":harfbuzz_shim",
+  ]
+  public_configs = [ ":system_harfbuzz" ]
+}
+
+config("pangoft2_link_hack") {
+}