Function callgraph_build 

pub fn callgraph_build(
    direct_edges_in: &str,
    indirect_sites_in: &str,
    pts_closure_in: &str,
    callgraph_out: &str,
) -> Program

Build a single-dispatch Program that OR-merges a direct call-edge bitset with the transitive-closure bitset produced by crate::points_to::andersen_points_to into the final callgraph edge bitset.

direct_edges_in and indirect_sites_in are read-only bitsets over node_count call-site lanes. pts_closure_in is the points-to closure for each indirect call-site. callgraph_out is the final bitset written lane-by-lane.

node_count is the number of call sites (one bit per site).