Implement "copy_bundle_data" tool without using a python script.

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 46 matching lines @@
 # proper input-dirty checking, but that could be expensive. Instead, use a
 # script to get the tool scripts' modification time to use as the version.
 # This won't cause a re-generation of GN files when the tool script changes
 # but it will cause edges to be marked as dirty if the ninja files are
 # regenerated. See https://crbug.com/619083 for details. A proper fix
 # would be to have inputs to tools (https://crbug.com/621119).
 tool_versions =
     exec_script("get_tool_mtime.py",
                 rebase_path([
                               "//build/toolchain/mac/compile_xcassets.py",
-                              "//build/toolchain/mac/copy_bundle_data.py",
                               "//build/toolchain/mac/filter_libtool.py",
                               "//build/toolchain/mac/linker_driver.py",
                             ],
                             root_build_dir),
                 "trim scope")
 
 # Work around for unused variable warning in template https://crbug.com/395883.
 assert(tool_versions != "")
 
 # Shared toolchain definition. Invocations should set toolchain_os to set the
@@ skipping 222 matching lines @@
     tool("stamp") {
       command = stamp_command
       description = stamp_description
     }
     tool("copy") {
       command = copy_command
       description = copy_description
     }
 
     tool("copy_bundle_data") {
-      if (is_ios) {
-        _extra_args = "--strings-format=binary1"
-      } else {
-        _extra_args = ""
+      # copy_command use hardlink if possible but this does not work with
+      # directories. If source is a directory, instead use "pax" to create
+      # the same tree structure using hardlinks to individual files (this
+      # preserve symbolic links too) as recommended in the replies to the
+      # question at http://serverfault.com/q/209888/43689 ("cp -al" isn't
+      # available on macOS).
+      #
+      # According to the man page for pax, the commands to use to clone
+      # olddir to newdir using pax are the following:
+      #
+      #   $ mkdir newdir
+      #   $ cd olddir
+      #   $ pax -rwl . ../newdir
+      #
+      # The _copydir command does exactly that but use an absolute path
+      # constructed using shell variable $OLDPWD (automatically set when
+      # cd is used) as computing the relative path is a bit complex and
+      # using pwd would requires a sub-shell to be created.
+      _copydir = "mkdir -p {{output}} && cd {{source}} && " +
+                 "pax -rwl . \"\$OLDPWD\"/{{output}}"
+      _command = "if [[ -d {{source}} ]]; then " + _copydir + "; else " +
+                 copy_command + "; fi"
+
+      # TODO(crbug.com/625578): Remove this conversion on iOS once all the
+      # bundle_data target have been fixed to reference converted files.
+      _convert_strings = is_ios
+      if (_convert_strings) {
+        _convert = "plutil -convert binary1 -o {{output}} {{source}}"
+        _command = "case {{source}} in " + "*.strings) " + _convert + ";; " +
+                   "*) " + _command + ";; esac"
       }
-      _tool = rebase_path("//build/toolchain/mac/copy_bundle_data.py",
-                          root_build_dir)
-      command = "TOOL_VERSION=${tool_versions.copy_bundle_data} python $_tool ${_extra_args} {{source}} {{output}}"
+
+      command = "rm -rf {{output}} && " + _command
       description = "COPY_BUNDLE_DATA {{source}} {{output}}"
       pool = ":bundle_pool($default_toolchain)"
     }
     tool("compile_xcassets") {
       _tool = rebase_path("//build/toolchain/mac/compile_xcassets.py",
                           root_build_dir)
       if (is_ios) {
         _sdk_name = ios_sdk_name
         _min_deployment_target = ios_deployment_target
       } else {
@@ skipping 44 matching lines @@
 
 mac_toolchain("ios_clang_x86") {
   toolchain_cpu = "x86"
   toolchain_os = "ios"
 }
 
 mac_toolchain("ios_clang_x64") {
   toolchain_cpu = "x64"
   toolchain_os = "ios"
 }