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

native_client_sdk/src/examples/fullscreen_tumbler/example.dsc

 {
   'TOOLS': ['newlib', 'pnacl'],
   'TARGETS': [
     {
-      'NAME' : 'fullscreen_tumbler',
-      'TYPE' : 'main',
-      'SOURCES' : [
+      'NAME': 'fullscreen_tumbler',
+      'TYPE': 'main',
+      'SOURCES': [
         'callback.h',
         'cube.cc',
         'cube.h',
         'opengl_context.cc',
         'opengl_context.h',
         'opengl_context_ptrs.h',
         'scripting_bridge.cc',
         'scripting_bridge.h',
         'shader_util.cc',
         'shader_util.h',
         'transforms.cc',
         'transforms.h',
         'tumbler.cc',
         'tumbler.h',
         'tumbler_module.cc'
       ],
-      'LIBS': ['ppapi_cpp', 'ppapi_gles2']
+      'LIBS': ['ppapi_gles2', 'ppapi_cpp', 'ppapi', 'pthread']
     }
   ],
   'DATA': [
     'bind.js',
     'check_browser.js',
     'dragger.js',
     'trackball.js',
     'tumbler.js',
     'vector3.js'
   ],
   'DEST': 'examples',
   'NAME': 'fullscreen_tumbler',
   'TITLE': 'Interactive Cube Example',
   'DESC': """
 This is a modified version of the Tumbler example above that supports
 full-screen display. It is in every way identical to Tumbler in
 functionality, except that it adds the ability to switch to/from
 full-screen display by pressing the Enter key.
 """,
   'INFO': 'Teaching focus: Full-screen.'
 }