Fix Mac build.

Change-Id: I316a3fefc62e706439fe0306e29b0ab42b3b116d
diff --git a/src/oatdump.cc b/src/oatdump.cc
index 5b9d271..1bbbb08 100644
--- a/src/oatdump.cc
+++ b/src/oatdump.cc
@@ -407,7 +407,7 @@
         if (run == 0) {
           StringAppendF(&summary, "\t%d: ", i);
         } else {
-          StringAppendF(&summary, "\t%d to %d: ", i, i + run);
+          StringAppendF(&summary, "\t%d to %zd: ", i, i + run);
           i = i + run;
         }
         Class* value_class = value == NULL ? obj_class->GetComponentType() : value->GetClass();