GN: Factor "stamp" and "copy" details out of toolchains

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/ios/ios_sdk.gni")
 
 assert(host_os == "mac")
 
 import("//build/toolchain/goma.gni")
+import("//build/toolchain/toolchain.gni")
 
 if (use_goma) {
   goma_prefix = "$goma_dir/gomacc "
 } else {
   goma_prefix = ""
 }
 
 # This will copy the gyp-mac-tool to the build directory. We pass in the source
 # file of the win tool.
 gyp_mac_tool_source =
@@ skipping 173 matching lines @@
       outfile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
       command = "$ld {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
       description = "LINK $outfile"
       rspfile_content = "{{inputs_newline}}"
       outputs = [
         outfile,
       ]
     }
 
+    # These two are really entirely generic, but have to be repeated in
+    # each toolchain because GN doesn't allow a template to be used here.
+    # See //build/toolchain/toolchain.gni for details.
     tool("stamp") {
-      command = "touch {{output}}"
-      description = "STAMP {{output}}"
+      command = stamp_command
+      description = stamp_description
     }
-
     tool("copy") {
-      command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
-      description = "COPY {{source}} {{output}}"
+      command = copy_command
+      description = copy_description
     }
 
     toolchain_args() {
       current_cpu = invoker.toolchain_cpu
       current_os = invoker.toolchain_os
 
       # These values need to be passed through unchanged.
       target_os = target_os
       target_cpu = target_cpu
 
@@ skipping 51 matching lines @@
 }
 
 mac_toolchain("x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
   cc = "${goma_prefix}/gcc"
   cxx = "${goma_prefix}/g++"
   ld = cxx
   is_clang = false
 }