Improves GN's make_global_settings

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.
 
 # Should only be running on Mac.
 assert(is_mac || is_ios)
 
 import("//build/toolchain/clang.gni")
 import("//build/toolchain/goma.gni")
 
 if (is_clang) {
   cc = rebase_path("//third_party/llvm-build/Release+Asserts/bin/clang", ".", root_build_dir)
   cxx = rebase_path("//third_party/llvm-build/Release+Asserts/bin/clang++", ".", root_build_dir)
 
   # Set the GYP header for all toolchains when running under Clang.
   if (is_gyp) {
-    gyp_header = make_clang_global_settings
+    gyp_header = "'make_global_settings': [" + make_clang_global_settings + "],"
   }
 } else {
   cc = "gcc"
   cxx = "g++"
 }
 ld = cxx
 
 # 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 58 matching lines @@
   #}
   tool("stamp") {
     command = "\${postbuilds}touch \$out"
     description = "STAMP \$out"
   }
   tool("copy") {
     command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
     description = "COPY \$in \$out"
   }
 }