gvmap plot_dot_polygons: squash -Wunused-variable warning in release mode

diff --git a/cmd/gvmap/make_map.c b/cmd/gvmap/make_map.c
index 2981180934e2744fb082e5cb463bf97e4bcc148e..b172c9839dc77ae812bb46a733841d2f68c351f2 100644 (file)
--- a/cmd/gvmap/make_map.c
+++ b/cmd/gvmap/make_map.c
@@ -294,6 +294,7 @@ static void plot_dot_polygons(agxbuf *sbuff, double line_width,
     np = 0;
     for (j = ia[i]; j < ia[i+1]; j++){
       assert(ja[j] < nverts && ja[j] >= 0);
+      (void)nverts;
       if (abs(a[j]) != ipoly){/* the first poly, or a hole */
        ipoly = abs(a[j]);
        if (r && g && b) {