Xcode archive fails when building ffmpeg from unity

I’m having a problem using mobile ffmpeg on ios via Unity. I’m using this asset: Unity_Bind_2, and its supposed to include everything needed for ios builds. On android everything works fine, however when archiving from xcode, I’m getting the following errors:

in Chrono.h at the lines using time_t

.
Error: Reference to unresolved using
decleration

    class _LIBCPP_TYPE_VIS system_clock
{
public:
    typedef microseconds                     duration;
    typedef duration::rep                    rep;
    typedef duration::period                 period;
    typedef chrono::time_point<system_clock> time_point;
    static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;

    static time_point now() _NOEXCEPT;
    static time_t     to_time_t  (const time_point& __t) _NOEXCEPT;
    static time_point from_time_t(time_t __t) _NOEXCEPT;
};

in __threading_support.h at lines using __libcpp_timespec_t

.
Error: Variable has incomplete type
‘__libcpp_timespec_t’

namespace __thread_detail {

inline __libcpp_timespec_t __convert_to_timespec(const chrono::nanoseconds& __ns)
{
  using namespace chrono;
  seconds __s = duration_cast<seconds>(__ns);
  __libcpp_timespec_t __ts;
  typedef decltype(__ts.tv_sec) __ts_sec;
  const __ts_sec __ts_sec_max = numeric_limits<__ts_sec>::max();

  if (__s.count() < __ts_sec_max)
  {
    __ts.tv_sec = static_cast<__ts_sec>(__s.count());
    __ts.tv_nsec = static_cast<decltype(__ts.tv_nsec)>((__ns - __s).count());
  }
  else
  {
    __ts.tv_sec = __ts_sec_max;
    __ts.tv_nsec = 999999999; // (10^9 - 1)
  }

  return __ts;
}

}

in __threading_support.h at lines using nanosleep

.
Error: use of undeclared identifier
‘nanosleep’

void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
{
   __libcpp_timespec_t __ts = __thread_detail::__convert_to_timespec(__ns);
   while (nanosleep(&__ts, &__ts) == -1 && errno == EINTR);
}

Some more details to understand the problem: for debugging purposes I opened an empty project with an empty scene and just added the plugin. Unity version: 2019.4.15f1 Player settings exactly like in the documentation

Does anyone have any idea? Thanks in advance!