$NetBSD$

Support Darwin/aarch64, from https://github.com/Homebrew/formula-patches.

--- configure
+++ configure
@@ -3518,6 +3518,8 @@ esac

 # Disable libffi for some systems.
 case "${target}" in
+  aarch64*-*-darwin2*)
+    ;;
   powerpc-*-darwin*)
     ;;
   i[3456789]86-*-darwin*)