datahub: Install cartopy & shapely from source
datahub: Install cartopy & shapely from source

So they link against the same version of geos.

We should probably move this to conda-forge at some point?
However, that'll probably bring in a lot of dependencies,
so don't wanna do that right now.

Fixes #1796

berkeley-dsep-infra/datahub,ryanlovett/datahub,berkeley-dsep-infra/datahub,berkeley-dsep-infra/datahub,ryanlovett/datahub,ryanlovett/datahub