OpenBSD has gone double-triple X as of mktemp.c r1.16
"Require that the template include at least 6 trailing Xs to match
POSIX mkstemp/mkdtemp.  Check before the call to mkstemp/mkdtemp
so we can give a better error message than "invalid argument"."

noticed by braddeicide https://github.com/yellowman/flashrd/issues/9