[NaCl SDK] Add arm gcc toolchain support to the SDK

native_client_sdk/src/libraries/nacl_mounts_test/example.dsc

 {
   # TODO(binji): pnacl doesn't build right now because gtest doesn't build yet.
-  'TOOLS': ['newlib', 'glibc', 'win'],
+  'TOOLS': ['newlib:x86', 'newlib:x64', 'glibc', 'win'],
 
   # Need to add ../../examples for common.js
   'SEARCH': ['.', '../../examples'],
   'TARGETS': [
     {
       'NAME' : 'nacl_mounts_test',
       'TYPE' : 'main',
       'SOURCES' : [
         'kernel_object_test.cc',
         'kernel_proxy_mock.h',
         'kernel_proxy_test.cc',
         'kernel_wrap_test.cc',
         'module.cc',
         'mount_node_test.cc',
         'mount_test.cc',
         'path_test.cc',
       ],
       'LIBS': ['ppapi', 'pthread', 'gtest', 'gmock', 'nacl_mounts', 'ppapi_cpp', 'gtest_ppapi']
     }
   ],
   'DATA': [
     'example.js'
   ],
   'DEST': 'tests',
   'NAME': 'nacl_mounts_test',
   'TITLE': 'NaCl Mounts test',
 }