Generate 3D Mesh from extruded Polygon

How to generate a 3D Mesh from a "2.5D" polygon with an additionally given extrusion? Preferably using a mature and well tested library in C++.

Background: I'm given a Geojson file which contains a simple type polygon geometry, including x,y,z data. I'm also given an "extrusion" parameter as part of the Feature Properties.

I was looking at CGAL, seems a good fit for the mesh generation. But I'm not sure about how to generate a geometry from the extruded 2.5D data, and I'm not sure what intermediate geometry type to use.