ffi_prep_closure is unavailable on ARM-based Macs

[timburks]

Nu builds fail on ARM-based Macs:

objc/NuBridge.m:1242:6: error: implicit declaration of function
      'ffi_prep_closure' is invalid in C99
      [-Werror,-Wimplicit-function-declaration]
        if (ffi_prep_closure(closure, cif, objc_calling_nu_method_handle...
            ^
1 error generated.
make: *** [objc/NuBridge.o] Error 1

This appears to be already fixed for iOS.

[NightMachinery]

Does it work via Rosetta?