Fix duplicated methods for POSIX platforms.

src/platform-posix.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 20 matching lines @@
 #if !defined(ANDROID)
 #include <cxxabi.h>
 #endif
 #include <stdio.h>
 
 #include "platform.h"
 
 namespace v8 {
 namespace internal {
 
-// Used by platform implementation files during OS::PostSetUp().
-void POSIXPostSetUp();
-
 // Used by platform implementation files during OS::DumpBacktrace()
 // and OS::StackWalk().
 template<int (*backtrace)(void**, int),
          char** (*backtrace_symbols)(void* const*, int)>
 struct POSIXBacktraceHelper {
   static void DumpBacktrace() {
     void* trace[100];
     int size = backtrace(trace, ARRAY_SIZE(trace));
     char** symbols = backtrace_symbols(trace, size);
     fprintf(stderr, "\n==== C stack trace ===============================\n\n");
@@ skipping 46 matching lines @@
 
     free(symbols);
 
     return frames_count;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_POSIX_H_