system calls on aarch64 darwin fail opaquely with llvm-{18,19}

[tkerber]

This may be related to #896, although I cannot tell.

Empirically, calls to the system procedure (for instance (system "echo foo")) fail on chez scheme 10.1.0 and 10.0.0 when compiled with llvm 18 / 19, but not with llvm 17. I have not observed this on aarch64 linux. Here's a sample repl transcript:

$ scheme
Chez Scheme Version 10.1.0
Copyright 1984-2024 Cisco Systems, Inc.

> (system "echo foo bar")
Exception in system: Resource temporarily unavailable
Type (debug) to enter the debugger.
> 

This was tested through nix, and currently affects the latest scheme obtainable on macos on nixos, though I'll make a PR to patch this downstream.