[PATCHv2] ntdll: Avoid truncating a nonzero exit code to zero in unix

[Marvin]

Hi,

While running your changed tests, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=52223

Your paranoid android.


=== debian9 (32 bit WoW report) ===

ntdll:
om.c:2116: Test failed: got 99