wihout O_DIRECT, pipe2 call was never made, hence the rval was
not written hence still '0' from a previous successful call. Then
the fallback to POSIX pipe wasn't called either.
Factor out the pipe2 creation and deal with all the platform
peculiarities in there.

Reported-by:  <lukas.zeller@plan44.ch>
Signed-off-by: Andreas Fenkart <andreas.fenkart@dev.digitalstrom.org>