In commit cbcf5bc64a90306c82f0eb99ae43b5f52c122f71, newer librsvg APIs were used that are not available in versions between 2.36.0 and 2.50.0, e.g. rsvg_handle_get_intrinsic_size_in_pixels which was included in 2.51.x.
This has been resolved by adding a HAVE_SVG_2_51 and using it for both rsvg_handle_get_intrinsic_size_in_pixels and rsvg_handle_render_document, though the later technically landed in 2.46.0.