Add option cc_wrapper to GN

build/toolchain/nacl/BUILD.gn

 # Copyright (c) 2014 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/sysroot.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/nacl_toolchain.gni")
 
 # Add the toolchain revision as a preprocessor define so that sources are
 # rebuilt when a toolchain is updated.
@@ skipping 36 matching lines @@
     scriptprefix = "cmd /c call "
     scriptsuffix = ".bat"
   } else {
     scriptprefix = ""
     scriptsuffix = ""
   }
 
   # When the compilers are run via goma or ccache rather than directly by
   # GN/Ninja, the goma/ccache wrapper handles .bat files but gets confused
   # by being given the scriptprefix.
-  if (host_os == "win" && !use_goma && !use_ccache) {
+  if (host_os == "win" && !use_goma && cc_wrapper == "") {
     compiler_scriptprefix = scriptprefix
   } else {
     compiler_scriptprefix = ""
   }
 
   nacl_toolchain(target_name) {
     toolchain_package = "pnacl_newlib"
     toolchain_revision = pnacl_newlib_rev
     toolchain_cpu = "pnacl"
     toolprefix =
@@ skipping 192 matching lines @@
   toolchain_tuple = "i686-nacl"
 }
 
 nacl_clang_toolchains("x64") {
   toolchain_tuple = "x86_64-nacl"
 }
 
 nacl_clang_toolchains("arm") {
   toolchain_tuple = "arm-nacl"
 }