Add sharp module building

[yosifkit]

Alpine 3.17 lib-vips is new enough for sharp

https://github.com/TryGhost/Ghost/blob/v5.65.1/yarn.lock#L28340-L28341
https://github.com/lovell/sharp/blob/v0.30.7/package.json#L157
https://pkgs.alpinelinux.org/packages?name=vips-dev&branch=v3.17

⬆️ this is a lot of manual checking to see which version of sharp that Ghost requires, and then which version of libvips that sharp requires, and then checking if that is available in the Alpine release we are on. I'd rather have some automation (in the Dockerfile?) to check these assumptions before just adding sharp back to the build-from-source deps.

Closes #293

[tianon]

Agreed, without something automated checking/verifying that whole chain of deps, this is not ideal. 😞