Build the atom cluster lookup after the packing is done

Author: MohamedElgammal

vpr/src/pack/pack.cpp

@@ -266,6 +266,7 @@ bool try_pack(t_packer_opts* packer_opts,
     /*       Use the re-cluster API to edit it        */
     /******************* Start *************************/
     VTR_LOG("Start the iterative improvement process\n");
+    init_clb_atoms_lookup(helper_ctx.atoms_lookup);
     //iteratively_improve_packing(*packer_opts, clustering_data, 2);
     VTR_LOG("the iterative improvement process is done\n");