Don't ask me for the reason why a straight-forward openat() call in
GNU tar ends up calling __openat_2() via the glibc. I don't know.
Anyway, that's the first time I had to ask something on StackOverflow,
and I was promptly pointed in the right direction!
<http://stackoverflow.com/questions/9161116/intercepting-the-openat-system-call-for-gnu-tar>