Fix IW4 fastfile writer factory steps

src/ZoneWriting/Writing/Steps/StepWriteTimestamp.cpp

@@ -0,0 +1,15 @@
+#include "StepWriteTimestamp.h"
+
+#include <algorithm>
+#include <ctime>
+
+StepWriteTimestamp::StepWriteTimestamp()
+{
+}
+
+void StepWriteTimestamp::PerformStep(ZoneWriter* zoneWriter, IWritingStream* stream)
+{
+    // time_t is not guaranteed to be 64bit so cast is necessary
+    const auto time = static_cast<int64_t>(std::time(nullptr));
+    stream->Write(&time, sizeof(time));
+}