Don't download the NaCl toolchain if GYP_DEFINES contains disable_nacl=1

BUG=none
TEST=manual


Review URL: http://codereview.chromium.org/8820022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113279 0039d316-1c4b-4281-b951-d872f2087c98

build/download_nacl_toolchains.py

@@ -10,6 +10,9 @@ import sys
 
 
 def Main(args):
+  # Exit early if disable_nacl=1.
+  if 'disable_nacl=1' in os.environ.get('GYP_DEFINES', ''):
+    return 0
   # Handle chromeos=1 specially (until its building its own toolchain).
   if 'chromeos=1' in os.environ.get('GYP_DEFINES', ''):
     args = [