[libc++] error: std::function does not support implementing fextl::move_only_function

[peppergrayxyz]

building using libc++ fails with:

FEX/FEXCore/include/FEXCore/fextl/functional.h:55:21: error: static assertion failed due to requirement 'noexcept(this->internal = std::move(wrapped_lambda))': This implementation of std::function does not support implementing fextl::move_only_function
   55 |       static_assert(noexcept(internal = std::move(wrapped_lambda)), "This implementation of std::function "
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
FEX/Source/Common/AsyncNet.h:253:7: note: in instantiation of function template specialization 'fextl::move_only_function<fasio::post_callback (fasio::error)>::move_only_function<(lambda at /home/pepper/dev/ghrepos/FEX/Source/Common/AsyncNet.h:253:7)>' requested here
  253 |       [ServerFD = FD, &Reactor = Reactor, OnAccept = std::move(OnAccept)](error ec) mutable {
      |       ^
1 error generated.