Fix build post a040967612.

contrib/libucl/src/ucl_msgpack.c

@@ -1247,7 +1247,7 @@ ucl_msgpack_consume (struct ucl_parser *parser)
 		if (len != 0) {
 			ucl_create_err (&parser->err,
 					"invalid non-empty container at the end; len=%zu",
-					(uintmax_t)len);
+					(size_t)len);
 
 			return false;
 		}