Turns out I'm not alone who spent considerable time fighting with CMake configuration issues. I ended up patching it to support a basic debug server protocol, so you could step through the CMakeLists.txt files in a debugger. In case anyone's interested, here's the CMake fork with debug support [0] and there's a detailed tutorial [1].
[0] https://github.com/sysprogs/cmake
[1] https://visualgdb.com/tutorials/cmake/debugger/