Build difficulties

[jricc]

Hello,
I'm trying to use Twist without using the VM supplied. But I'm having a few installation difficulties.
The first was like this:

File "src/sim.ml", line 59, characters 13-30:
59 |     let s0 = Unix.gettimeofday () in
                  ^^^^^^^^^^^^^^^^^
Error: Unbound value Unix.gettimeofday

I fixed it by replaced Unix with Core_unix.
The second is:

File "src/sim.ml", line 9, characters 44-56:
9 | let empty () = Qpp.empty (), Hashtbl.create (module Int)
                                                ^^^^^^^^^^^^
Error: This expression is packed module, but the expected type is int

Could you help me ?