Common: DragonFly needs MAP_NOSYNC as well

Common/MemArena.cpp

@@ -189,7 +189,7 @@ void *MemArena::CreateView(s64 offset, size_t size, void *base)
 // Do not sync memory to underlying file. Linux has this by default.
 #ifdef BLACKBERRY
 		MAP_NOSYNCFILE |
-#elif defined(__FreeBSD__)
+#elif defined(__DragonFly__) || defined(__FreeBSD__)
 		MAP_NOSYNC |
 #endif
 		((base == 0) ? 0 : MAP_FIXED), fd, offset);