[NaCl SDK] Remove newlib toolchain from the SDK

native_client_sdk/src/examples/tutorial/debugging/example.dsc

 {
   'DISABLE_PACKAGE': True,  # Doesn't work in packaged apps yet.
-  'TOOLS': ['newlib'],
+  'TOOLS': ['clang-newlib'],
   'TARGETS': [
     {
       'NAME' : 'debugging',
       'TYPE' : 'main',
       'SOURCES' : [
         'debugging.c',
       ],
       'CFLAGS': ['-fno-omit-frame-pointer'],
       'DEPS' : ['error_handling'],
       'LIBS' : ['error_handling', 'ppapi', 'pthread']
     }
   ],
   'DATA': [
     'example.js',
   ],
   'DEST': 'examples/tutorial',
   'NAME': 'debugging',
   'TITLE': 'Debugging',
   'GROUP': 'Tutorial'
 }