Implement "copy_bundle_data" tool without using a python script.

build/toolchain/mac/BUILD.gn

Index: build/toolchain/mac/BUILD.gn
diff --git a/build/toolchain/mac/BUILD.gn b/build/toolchain/mac/BUILD.gn
index 231a546891d463367ebcdce18584116f5d5f92fa..a5ff08faffad70413eba86ad297d98e48531be61 100644
--- a/build/toolchain/mac/BUILD.gn
+++ b/build/toolchain/mac/BUILD.gn
@@ -64,7 +64,6 @@ 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",
                             ],
@@ -307,14 +306,39 @@ template("mac_toolchain") {
     }
 
     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)"
     }