Ah ok, Do you think Fpcupdeluxe can do the job of building a cross compiler from Windows to aarch64-freebsd ?
Thanks to you @PascalDragon.
It will refuse to build this combination (at least on Linux). I can build x86_64/FreeBSD and I can build aarch64/Linux but it will not allow to select aarch64/FreeBSD. I could not test this on Windows at the moment, maybe it has to do with the availability of cross binutils and the situation is different on Windows. You could just download the tool and try it yourself (I generally highly recommend it), it won't break anything on your current installation, it will compile a completely isolated installation, all contained inside one folder, including all config and settings files.
Maybe you should also ask the author of fpcupdeluxe about what the reason is, maybe he just did not yet add it to the whitelist, he is usually very quickly responding and always trying his best to fix bugs, often on the same day you report it.