Fox goma on Windows for the GN build.

This properly defines the goma wrapper. Previously these were not wrapped with the make_global_settings dictionary.

TBR=scottmg
BUG=

Review URL: https://codereview.chromium.org/140653010

git-svn-id: http://src.chromium.org/svn/trunk/src/build@245763 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

toolchain/win/BUILD.gn

@@ -24,7 +24,7 @@ copy_command = "$python_path gyp-win-tool recursive-mirror \$in \$out"
 
 if (use_goma) {
   # Add the Goma compiler prefixes to the GYP file.
-  gyp_header = make_goma_global_settings
+  gyp_header = "'make_global_settings': [ $make_goma_global_settings ],"
 }
 
 # 32-bit toolchain -------------------------------------------------------------