[gn] Enable stricter build flags

src/base/platform/platform-win32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for Win32.
 
 // Secure API functions are not available using MinGW with msvcrt.dll
 // on Windows XP. Make sure MINGW_HAS_SECURE_API is not defined to
 // disable definition of secure API functions in standard headers that
 // would conflict with our own implementation.
@@ skipping 798 matching lines @@
 
 
 void OS::Guard(void* address, const size_t size) {
   DWORD oldprotect;
   VirtualProtect(address, size, PAGE_NOACCESS, &oldprotect);
 }
 
 void OS::Unprotect(void* address, const size_t size) {
   LPVOID result = VirtualAlloc(address, size, MEM_COMMIT, PAGE_READWRITE);
   DCHECK_IMPLIES(result != nullptr, GetLastError() == 0);
+  USE(result);
 }
 
 void OS::Sleep(TimeDelta interval) {
   ::Sleep(static_cast<DWORD>(interval.InMilliseconds()));
 }
 
 
 void OS::Abort() {
   if (g_hard_abort) {
     V8_IMMEDIATE_CRASH();
@@ skipping 563 matching lines @@
 
 
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   BOOL result = TlsSetValue(static_cast<DWORD>(key), value);
   USE(result);
   DCHECK(result);
 }
 
 }  // namespace base
 }  // namespace v8