On mips64le, syscall.Getdents() and struct syscall.Dirent do
not fit together, causing our Getdents implementation to
return garbage ( https://github.com/rfjakob/gocryptfs/issues/200
and https://github.com/golang/go/issues/23624 ).
Switch to unix.Getdents which does not have this problem -
the next Go release with the syscall package fixes is too
far away, and will take time to trickle into distros.
26ba8103bf