[NaCl SDK] Remove newlib toolchain from the SDK

native_client_sdk/src/libraries/error_handling/library.dsc

 {
-  'TOOLS': ['newlib', 'clang-newlib'],
+  'TOOLS': ['clang-newlib'],
   'TARGETS': [
     {
       'NAME' : 'error_handling',
       'TYPE' : 'lib',
       'SOURCES' : [
         "error_handling.c",
         "string_stream.c"
       ],
     }
   ],
   'HEADERS': [
     {
       'FILES': [
         "error_handling.h",
         "string_stream.h",
       ],
       'DEST': 'include/error_handling',
     },
   ],
   'DEST': 'src',
   'NAME': 'error_handling',
 }