Hey, thanks for your great effort in this project and I apologize ahead if my issue is not an issue :).

With the recent 3.9-slim, after merging #980 , the --with-system-expat flag was removed along with libexpat-dev, this causes all my images to break since a requirement I use extensively , fiona, needs it.

Assuming this change is mandatory, I would be happy for a solution, workaround or whatever can help me get through it. Many thanks!