chore: add shell flag to prepare script

[nbbeeken]

This should fix the script failing to run on windows.

I had added this flag in earlier work when we wanted a more complex prepare script but we abandoned that, however we should still keep this flag to fix windows use cases.

[emadum]

This does in fact fix it, I also made this change in #2633 but happy to merge it in separately!

One question, is there any harm to passing {shell: true} on platforms other than Windows?

[nbbeeken]

One question, is there any harm to passing {shell: true} on platforms other than Windows?

No harm, but someone astutely made the point that it adds expense where none is needed, I was inclined to agree. I'll merge this now just to unblock those using the git link dep style, we can simplify it back to shell: true in your PR if we wish. :) ty for speedy ✅