Set config vars for darwin in configure_cross

[brendanzab]

This ends up just being the same as for FreeBSD 13.0 x86-64.

When matching on the host triple, I used autotools’ conventions of aarch64-*darwin*, as opposed to clang's arm64-*darwin*. I hope thats ok! Perhaps if we wanted to be more careful we could call config.sub on the triple before making use of it.

[wangp]

Thanks Brendan. I'll merge the script change.

I'm not convinced about the markdown changes. I specifically write markdown like that so it looks good in unrendered form.

[brendanzab]

Ah that's fair enough – understandably different priorities. I generally write for the rendered form which is a bit of a different use case. 😅