[NaCL SDK] Add initial support for nacl-clang

native_client_sdk/src/tests/sdk_util_test/example.dsc

 {
-  'TOOLS': ['newlib', 'glibc', 'pnacl', 'linux', 'mac'],
+  'TOOLS': ['newlib', 'glibc', 'pnacl', 'linux', 'mac', 'clang-newlib'],
   'SEL_LDR': True,
 
   'TARGETS': [
     {
       'NAME' : 'sdk_util_test',
       'TYPE' : 'main',
       'SOURCES' : [
         'main.cc',
         'string_util_test.cc',
       ],
       'DEPS': ['ppapi_simple', 'sdk_util', 'nacl_io'],
       # Order matters here: gtest has a "main" function that will be used if
       # referenced before ppapi.
       'LIBS': ['ppapi_simple', 'sdk_util', 'ppapi', 'gtest', 'nacl_io', 'gmock', 'ppapi_cpp', 'pthread'],
       'CXXFLAGS': ['-Wno-sign-compare']
     }
   ],
   'DATA': [
     'example.js'
   ],
   'DEST': 'tests',
   'NAME': 'sdk_util_test',
   'TITLE': 'SDK Util test',
 }