[Bug c++/80469] Undefined symbol for abstract class impl with -fvisibility=hidden

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80469

--- Comment #2 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
In other words, don't use -fvisibility=hidden when you build subimpl.cpp.