build: no bindings: make error more explicit

[Frankkkkk]

Hi,

The panic that arises when there are no pre-build bindings available is not that explicit and may confuse some users into thinking there's something wrong with GDAL.

Thanks!

• [x] I agree to follow the project's code of conduct.

• [x] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

[lnicola]

Thanks! Maybe we should go for something simpler like "Enable the bindgen feature of gdal or gdal-sys to generate them during build."?

[Frankkkkk]

Disclaimer: I know nothing about gdal-rs ;-)

I think it'd be great to distinguish GDAL from the rust crate. To be honest I thought the message was related to the gdal library. Maybe something like "Enable the bindgen feature of the gdal or gdal-sys crate to generate them during build."?

If that's okay with you I can change the MR. Thanks!

[lnicola]

I mean sure, but GDAL is GDAL and gdal is this crate :-).