I'm closing this because I asked in the wxwidgets irc and apparently
there is no bug and 'lib/wx/include/gtk3-unicode-3.1/wx/setup.h' is
indeed the correct install location. The guix package currently installs
it there.
The problem I had with my WIP trenchbroom package was that trenchbroom
called
Hello, wxwidgets does not install 'include/wx/setup.h' with the install
target.
I'm packaging Trenchbroom and it requires this file. From the error
messages I think some other wxwidgets headers also cross reference it.
For a workaround I copied it from
'lib/wx/include/gtk3-unicode-3.1/wx/setup.h'
