Conclusion
==========
All in all, I see the following possible solutions. Maybe some of
them don't work, but at least they're worth a try. Please give your
opinion on each point, and don't hesitate to add other suggestions.
Static libraries:
(A) Fix GTK to find their symbols in (statically linked) EXE files.
(B) Find a way to build GTK as shared library, but everything else
as static library.
(C) Don't change anything and rely on the developers to put their
application and libraries into one big DLL to be used with a
small runner EXE.
(D) Don't change anything and rely on the developers to download
the official GTK win32 development packages.
Shared libraries:
(E) Rewrite mingw-cross-env to build everything as shared libraries,
building own DLL files on the way.
(F) Rewrite mingw-cross-env to build everything as shared stub
libraries, to be used with the official project DLLs.
Greets,
Volker