Don't use mprotect on Cygwin

src/platform-posix.cc

 // Copyright 2011 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 52 matching lines @@
 // limit.
 
 intptr_t OS::MaxVirtualMemory() {
   struct rlimit limit;
   int result = getrlimit(RLIMIT_DATA, &limit);
   if (result != 0) return 0;
   return limit.rlim_cur;
 }
 
 
+#ifndef __CYGWIN__
 // Get rid of writable permission on code allocations.
 void OS::ProtectCode(void* address, const size_t size) {
   mprotect(address, size, PROT_READ | PROT_EXEC);
 }
 
 
 // Create guard pages.
 void OS::Guard(void* address, const size_t size) {
   mprotect(address, size, PROT_NONE);
 }
+#endif  // __CYGWIN__
 
 
 // ----------------------------------------------------------------------------
 // Math functions
 
 double modulo(double x, double y) {
   return fmod(x, y);
 }
 
 
@@ skipping 362 matching lines @@
   return ntohl(value);
 }
 
 
 Socket* OS::CreateSocket() {
   return new POSIXSocket();
 }
 
 
 } }  // namespace v8::internal