libsel4vka: fix format string 32-bit compatability
diff --git a/libsel4vka/include/vka/object.h b/libsel4vka/include/vka/object.h
index 5b06aa9..56c477d 100644
--- a/libsel4vka/include/vka/object.h
+++ b/libsel4vka/include/vka/object.h
@@ -44,7 +44,7 @@
     int error = -1;
     if (!(type < seL4_ObjectTypeCount)) {
         result->cptr = 0;
-        ZF_LOGE("Unknown object type: %lu", type);
+        ZF_LOGE("Unknown object type: %ld", (long) type);
         goto error;
     }