CBMC doesn't have a model for `clockid_t` and `clock_gettime`

[feliperodri]

CBMC version: 5.80.0
Operating system: N/A

I tried to verify this C program:

uint32_t my_time(void)
{
    struct timespec t;
    clock_gettime(CLOCK_MONOTONIC, &t);
    return (t.tv_nsec / 1000000) + ( (t.tv_sec % 86400) * 1000);
}

but there is no model for clock_gettime in CBMC. I tried to write a stub following the specification, but there was no model for clockid_t either. Adding this issue to add this model at some point.