add glibc support to examples

native_client_sdk/src/examples/hello_world_gles/example.dsc

 {
-  'TOOLS': ['newlib', 'pnacl', 'win'],
+  'TOOLS': ['newlib', 'glibc', 'pnacl', 'win'],
   'TARGETS': [
     {
       'NAME' : 'hello_world_gles',
       'TYPE' : 'main',
       'SOURCES' : ['hello_world.cc', 'matrix.cc', 'matrix.h'],
       'CXXFLAGS': [
         '$(NACL_CXXFLAGS)', 
         '-I../../src',
         '-I../../src/ppapi/lib/gl'
       ],
       'LIBS': ['ppapi_gles2', 'ppapi', 'pthread']
     }
   ],
   'DATA': [
     'fragment_shader_es2.frag',
     'hello.raw',
     'vertex_shader_es2.vert'
   ],
   'DEST': 'examples',
   'NAME': 'hello_world_gles',
   'TITLE': 'Hello World GLES 2.0',
   'DESC': """
 The Hello World GLES 2.0 example demonstrates how to create a 3D cube
 that rotates.  This is a simpler example than the tumbler example, and 
 written in C.  It loads the assets using URLLoader.""",
   'INFO': 'Teaching focus: 3D graphics, URL Loader.'
 }