Make use of -lppapi explicit to allow for correct library order.

native_client_sdk/src/examples/debugging/example.dsc

 {
   'TOOLS': ['newlib'],
   'TARGETS': [
     {
       'NAME' : 'debugging',
       'TYPE' : 'main',
       'SOURCES' : [
         'hello_world.c', 
         'string_stream.c', 
         'string_stream.h',
         'untrusted_crash_dump.c',
         'untrusted_crash_dump.h'
       ],
-      'CCFLAGS': ['$(NACL_CCFLAGS)', '-fno-omit-frame-pointer']
+      'CCFLAGS': ['$(NACL_CCFLAGS)', '-fno-omit-frame-pointer'],
+      'LIBS' : ['ppapi', 'pthread']
     }
   ],
   'POST': 'include Makefile.inc\n',
   'DATA': ['Makefile.inc'],
   'DEST': 'examples',
   'NAME': 'debugging',
   'TITLE': 'Debugging',
   'DESC': """
 Debugging example shows how to use developer only features to enable
 catching an exception, and then using that to create a stacktrace.""",
   'INFO': 'Debugging, Stacktraces.'
 
 }