Fix build with system harfbuzz

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") {
+group("harfbuzz-ng") {
+  public_deps = [
+    ":harfbuzz-ng-ft",
+    ":harfbuzz-ng-without-freetype",
+  ]
+}
+
+source_set("harfbuzz-ng-ft") {
   deps = [
     ":harfbuzz_shim",
   ]
+  public_configs = [ ":system_harfbuzz" ]
+}
+
+source_set("harfbuzz-ng-without-freetype") {
+  deps = [
+    ":harfbuzz_shim",
+  ]
   public_configs = [ ":system_harfbuzz" ]
 }
 
 config("pangoft2_link_hack") {
 }