Hook up the link pool in the GN build.

build/toolchain/gcc_toolchain.gni

 # Copyright (c) 2013 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.
 
+# This value will be inherited in the toolchain below.
+concurrent_links = exec_script("get_concurrent_links.py", [], "value")
+
 # This template defines a toolchain for something that works like gcc
 # (including clang).
 #
 # It requires the following variables specifying the executables to run:
 #  - cc
 #  - cxx
 #  - ar
 #  - ld
 # and the following which is used in the toolchain_args
 #  - toolchain_cpu_arch  (What "cpu_arch" should be set to when invoking a
@@ skipping 179 matching lines @@
       if (defined(invoker.is_clang)) {
         is_clang = invoker.is_clang
       }
     }
 
     if (defined(invoker.deps)) {
       deps = invoker.deps
     }
   }
 }