Switch to rabs according to version 5.1.1 tag...

Switch to rabs according to version 5.1.1 tag (https://github.com/KarypisLab/METIS/blob/v5.1.1-DistDGL-v0.5/libmetis/balance.c)

3rdParty/metis/metis-5.1.0/libmetis/balance.c

@@ -20,7 +20,7 @@ void Balance2Way(ctrl_t *ctrl, graph_t *graph, real_t *ntpwgts)
 
   if (graph->ncon == 1) {
     /* return right away if the balance is OK */
-    if (abs(ntpwgts[0]*graph->tvwgt[0]-graph->pwgts[0]) < 3*graph->tvwgt[0]/graph->nvtxs)
+    if (rabs(ntpwgts[0]*graph->tvwgt[0]-graph->pwgts[0]) < 3*graph->tvwgt[0]/graph->nvtxs)
       return;
 
     if (graph->nbnd > 0)