Followup to 'Scripts to upload and update the mac toolchain.'

build/gyp_environment.py

Index: build/gyp_environment.py
diff --git a/build/gyp_environment.py b/build/gyp_environment.py
index fb50645d56fc5adc4276f9ac989a06059c4c4aa3..62c283bfb6051a21a3dfd1acff56ad3aaa380ff4 100644
--- a/build/gyp_environment.py
+++ b/build/gyp_environment.py
@@ -9,6 +9,7 @@ make sure settings are consistent between them, all setup should happen here.
 """
 
 import gyp_helper
+import mac_toolchain
 import os
 import sys
 import vs_toolchain
@@ -31,3 +32,6 @@ def SetEnvironment():
     os.environ['GYP_GENERATORS'] = 'ninja'
 
   vs_toolchain.SetEnvironmentAndGetRuntimeDllDirs()
+  mac_toolchain_dir = mac_toolchain.GetToolchainDirectory()
+  if mac_toolchain_dir:
+     os.environ['DEVELOPER_DIR'] = mac_toolchain_dir