[Bug c++/77886] -Wimplicit-fallthrough: breaks duff's device (in function templates)

[marc.mutz at kdab dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77886

--- Comment #10 from Marc Mutz <marc.mutz at kdab dot com> ---
I can confirm patch fixes my Qt build, ie. not just bug.cpp.

Thanks!