Use xtask to build `bindings/apple`

[jplatte]

We have a few .sh scripts in bindings/apple. I think they are complicated enough to warrant being replaced by an xtask subcommand.

👍🏼 / 👎🏼 @poljar @gnunicorn @Hywan ?

[poljar]

I was going to ask if we could get rid of the scripts in #985. So yes from me.

[gnunicorn]

they are mostly for @stefanceriu and his team, so we'd have to level with him about that...

[stefanceriu]

I would say we have no attachment to bash and hopefuly everything can be moved over to xtask. Now, planning wise, this wouldn't be very high up on our list atm and your help migrating them would be greatly appreciated.

[Hywan]

The more unified solutions for tasks we have, the better. So I'm all in favor of moving it to xtask.