Funny/sad that this possibility took me so long to realize. Until now it
was "you can have command-line utilities or static plugins but never
both", and only with CMake 3.13+ it was possible to link static plugins
to these executables from outside. Now it's a builtin and supported
option.
Similar to the change done in Corrade, see the commit for details:
878624ac36
Wow, this is probably the most backwards-compatibility code I've ever
written. Can't wait until I can drop all that.
It limits the support for CMake 3.12+, but it's much less verbose and I
don't expect people to use ancient CMake versions with IDEs like Xcode
or VS anyway, so this should be fine.
Currently those will be needed mainly by the Vk library to patch around
a SwiftShader bug. I'm not sure yet how the public API should look so
it's all hidden in the Implementation namespace for now.