Common: Add utility function that wraps localtime_s() or localtime_t().

Source/Core/Common/TimeUtil.cpp

@@ -0,0 +1,24 @@
+// Copyright 2024 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/TimeUtil.h"
+
+#include <ctime>
+#include <optional>
+
+namespace Common
+{
+std::optional<std::tm> Localtime(std::time_t time)
+{
+  std::tm local_time;
+#ifdef _MSC_VER
+  if (localtime_s(&local_time, &time) != 0)
+    return std::nullopt;
+#else
+  std::tm* result = localtime_r(&time, &local_time);
+  if (result != &local_time)
+    return std::nullopt;
+#endif
+  return local_time;
+}
+}  // Namespace Common