Don't use mprotect on Cygwin

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 5f283c3571510f3ae005e57f29bf170d186ed6d3..85a5e4f610d09c543057a249b4c09a9ac1224027 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -166,6 +166,18 @@ void OS::Free(void* address, const size_t size) {
 }
 
 
+void OS::ProtectCode(void* address, const size_t size) {
+  DWORD old_protect;
+  VirtualProtect(address, size, PAGE_EXECUTE_READ, &old_protect);
+}
+
+
+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);