Use explicit pool to define concurrent_links jobs.

build/toolchain/mac/BUILD.gn

 # 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.
 
 # TODO(brettw) Use "gcc_toolchain.gni" like the Linux toolchains. This requires
 # some enhancements since the commands on Mac are slightly different than on
 # Linux.
 
 import("../goma.gni")
 import("//build/config/clang/clang.gni")
@@ skipping 52 matching lines @@
 
 # Shared toolchain definition. Invocations should set toolchain_os to set the
 # build args in this definition.
 template("mac_toolchain") {
   toolchain(target_name) {
     assert(defined(invoker.toolchain_cpu),
            "mac_toolchain() must specify a \"toolchain_cpu\"")
     assert(defined(invoker.toolchain_os),
            "mac_toolchain() must specify a \"toolchain_os\"")
 
-    # concurrent_links is picked up from the declare_arg().
-
     if (use_goma) {
       assert(cc_wrapper == "", "Goma and cc_wrapper can't be used together.")
       _compiler_prefix = "$goma_dir/gomacc "
     } else if (cc_wrapper != "") {
       _compiler_prefix = cc_wrapper + " "
     } else {
       _compiler_prefix = ""
     }
 
     if (invoker.toolchain_os != "ios" || !use_xcode_clang) {
@@ skipping 105 matching lines @@
         "{{output_dir}}/{{target_output_name}}{{output_extension}}",
       ]
       default_output_dir = "{{target_out_dir}}"
       default_output_extension = ".a"
       output_prefix = "lib"
     }
 
     tool("solink") {
       dylib = "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # eg "./libfoo.dylib"
       rspfile = dylib + ".rsp"
+      pool = "//build/toolchain:link_pool($default_toolchain)"
 
       # These variables are not built into GN but are helpers that implement
       # (1) linking to produce a .dylib, (2) extracting the symbols from that
       # file to a temporary file, (3) if the temporary file has differences from
       # the existing .TOC file, overwrite it, otherwise, don't change it.
       #
       # As a special case, if the library reexports symbols from other dynamic
       # libraries, we always update the .TOC and skip the temporary file and
       # diffing steps, since that library always needs to be re-linked.
       tocname = dylib + ".TOC"
@@ skipping 43 matching lines @@
         outputs += [ _dsym_output ]
       }
       if (_save_unstripped_output) {
         outputs += [ _unstripped_output ]
       }
     }
 
     tool("solink_module") {
       sofile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # eg "./libfoo.so"
       rspfile = sofile + ".rsp"
+      pool = "//build/toolchain:link_pool($default_toolchain)"
 
       link_command = "$linker_driver $ld -bundle {{ldflags}} -o \"$sofile\" -Wl,-filelist,\"$rspfile\""
       if (is_component_build) {
         link_command += " -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
       }
       link_command += dsym_switch
       link_command += " {{solibs}} {{libs}}"
       command = link_command
 
       rspfile_content = "{{inputs_newline}}"
@@ skipping 14 matching lines @@
         outputs += [ _dsym_output ]
       }
       if (_save_unstripped_output) {
         outputs += [ _unstripped_output ]
       }
     }
 
     tool("link") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
+      pool = "//build/toolchain:link_pool($default_toolchain)"
 
       # Note about --filelist: Apple's linker reads the file list file and
       # interprets each newline-separated chunk of text as a file name. It
       # doesn't do the things one would expect from the shell like unescaping
       # or handling quotes. In contrast, when Ninja finds a file name with
       # spaces, it single-quotes them in $inputs_newline as it would normally
       # do for command-line arguments. Thus any source names with spaces, or
       # label names with spaces (which GN bases the output paths on) will be
       # corrupted by this process. Don't use spaces for source files or labels.
       command = "$linker_driver $ld $dsym_switch {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
@@ skipping 108 matching lines @@
   mac_toolchain("ios_clang_x86") {
     toolchain_cpu = "x86"
     toolchain_os = "ios"
   }
 
   mac_toolchain("ios_clang_x64") {
     toolchain_cpu = "x64"
     toolchain_os = "ios"
   }
 }