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

ports/ruby-ppapi/main.c

 /* Copyright (c) 2013 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. */
 
 #undef RUBY_EXPORT
 #include <ruby.h>
 #include <spawn.h>
 #include <stdio.h>
 
 #include "nacl_main.h"
 
 #ifdef __x86_64__
 #define NACL_ARCH "x86_64"
 #elif defined __i386__
 /*
  * Use __i386__ rather then __i686__ since the latter is not defined
  * by i686-nacl-clang.
  */
 #define NACL_ARCH "x86_32"
 #elif defined __arm__
 #define NACL_ARCH "arm"
 #elif defined __pnacl__
 #define NACL_ARCH "pnacl"
 #else
 #error "unknown arch"
 #endif
 
 #define DATA_ARCHIVE "rbdata-" NACL_ARCH ".tar"
 
-int nacl_main(int argc, char** argv) {
+int main(int argc, char** argv) {
   if (nacl_startup_untar(argv[0], DATA_ARCHIVE, "/"))
     return -1;
 
   if (argc == 2 && !strcmp(argv[1], "/bin/irb"))
     fprintf(stderr, "Launching irb ...\n");
   ruby_sysinit(&argc, &argv);
   {
     RUBY_INIT_STACK;
     ruby_init();
     return ruby_run_node(ruby_options(argc, argv));
   }
 }