https://bugs.winehq.org/show_bug.cgi?id=49896
--- Comment #4 from Rafał Mużyło galtgendo@o2.pl ---
I'm using Gentoo Linux with debug symbols enabled for app-emulation/wine-staging, so I'm not sure why debug info isn't showing up properly.
I haven't rechecked it lately, but awhile ago wine just failed at split-debug (.gnu_debuglink). There were supposed to be improvements since (quite a few commits awhile ago), but perhaps something was missed.