https://bugs.winehq.org/show_bug.cgi?id=49637
--- Comment #13 from Mike Lothian mike@fireburn.co.uk --- Apologies, you're right about the dlls vs dlls.so - I'm getting the same mix between the two builds - so sorry for the noise about that issue :$
Gentoo's portage always uses fresh files for it's builds. I personally use tmpfs for my build directory - maybe the lack of debugging (-g -gdwarf-2 -gstrict-dwarf) combined with tmpfs, and a fresh build environment highlights a race issue?