V8: Don't use mprotect on Cygwin as virtual memory is managed directly via WinAPI calls.

Upstream fix: http://codereview.chromium.org/7549009

deps/v8/src/platform-cygwin.cc

@@ -166,6 +166,12 @@ void OS::Free(void* address, const size_t size) {
 }
 
 
+void OS::Guard(void* address, const size_t size) {
+  DWORD oldprotect;
+  VirtualProtect(address, size, PAGE_READONLY | PAGE_GUARD, &oldprotect);
+}
+
+
 void OS::Sleep(int milliseconds) {
   unsigned int ms = static_cast<unsigned int>(milliseconds);
   usleep(1000 * ms);

deps/v8/src/platform-posix.cc

@@ -70,10 +70,12 @@ intptr_t OS::MaxVirtualMemory() {
 }
 
 
+#ifndef __CYGWIN__
 // Create guard pages.
 void OS::Guard(void* address, const size_t size) {
   mprotect(address, size, PROT_NONE);
 }
+#endif  // __CYGWIN__
 
 
 // ----------------------------------------------------------------------------