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

native_client_sdk/src/examples/input_events/example.dsc

 {
   'TOOLS': ['newlib', 'glibc', 'pnacl', 'win'],
   'TARGETS': [
     {
       'NAME' : 'input_events',
       'TYPE' : 'main',
       'SOURCES' : ['input_events.cc'],
-      'LIBS': ['ppapi_cpp']
+      'LIBS': ['ppapi_cpp', 'ppapi', 'pthread']
     }
   ],
   'DEST': 'examples',
   'NAME': 'input_events',
   'TITLE': 'Input Events',
   'DESC': """
 The Input Events example demonstrates how to handle events triggered by
 the user. This example allows a user to interact with a square representing a
 module instance. Events are displayed on the screen as the user clicks,
 scrolls, types, inside or outside of the square.""",
   'INFO': 'Keyboard and mouse input, view change, and focus events.'
 }