Switch from using 'nacl_main' to 'main' entry point

build_tools/pnacl-configure-shim.py

 #!/usr/bin/env python
 # Copyright (c) 2014 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Autoconf builds lots of small executables.
 This wreaks havock with pnacl's slow -O2 build time.
 Additionally linking nacl_io + ppapi_simple slows things down even more.
 
 This script is injected for CC to speed up configure by:
 - When configuring:
   - Drop -O2 and -O3
   - Add -O0
   - Drop nacl_spawn + nacl_io + cli_main and their dependencies.
 """
 
 import subprocess
 import sys
 
 cmd = sys.argv[1:]
 configuring = 'conftest.c' in cmd or 'conftest.pexe' in cmd
 
 DROP_FLAGS = {
     '-O2',
     '-O3',
-    '-Dmain=nacl_main',
     '-Dmain=SDL_main',
     '-lnacl_io',
     '-lnacl_spawn',
     '-lppapi_simple',
     '-lppapi_cpp',
     '-lppapi',
     '-lcli_main',
     '-lSDLmain',
 }
 
 if configuring:
   cmd = [i for i in cmd if i not in DROP_FLAGS]
   cmd += ['-O0']
 
 sys.exit(subprocess.call(cmd))