Add android_libcpp_lib_dir gn arg

build/android/BUILD.gn

 # Copyright 2014 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/android/rules.gni")
 import("//third_party/ijar/ijar.gni")
 
 sun_tools_jar_path = "$root_gen_dir/sun_tools_jar/tools.jar"
 
 # Create or update the API versions cache if necessary by running a
@@ skipping 26 matching lines @@
 
 generate_interface_jar("android_ijar") {
   input_jar = android_sdk_jar
   output_jar = "$root_out_dir/lib.java/android.interface.jar"
 }
 
 # Copy to the lib.unstripped directory so that gdb can easily find it.
 copy("cpplib_unstripped") {
   _soname = "libc++_shared.so"
   sources = [
-    "${android_libcpp_root}/libs/${android_app_abi}/${_soname}",
+    "${android_libcpp_lib_dir}/${_soname}",
   ]
   outputs = [
     "${root_out_dir}/lib.unstripped/${_soname}",
   ]
 }
 
 action("cpplib_stripped") {
   _strip_bin = "${android_tool_prefix}strip"
   _soname = "libc++_shared.so"
   _input_so = "${root_out_dir}/lib.unstripped/${_soname}"
@@ skipping 68 matching lines @@
   _target_name = get_path_info(script, "name") + "_wrapper"
   _wrapper_targets += [ ":$_target_name" ]
   wrapper_script(_target_name) {
     target = script
   }
 }
 
 group("wrapper_scripts") {
   deps = _wrapper_targets
 }