Thanks for the help everyone.
I got frustrated and deleted the directory/workspace, made a new copy and did it all over again. This time I never changed the environment (stayed with x64, MSBuild Tools and the same version of the compiler the whole time). For some reason it's working now.
I guess I messed up some directive creating the lib files, maybe using an old outdated SDK. Its also possible my VS Code extension did not update all the binaries during rebuild ( I switched from Release (x86) to Release (x64) several times). The c++ and cmake extensions for VS Code is not always on point it seems. And to be fair, me manually editing the makefiles was probably not helping. But its all good now
You really shouldn't be manually calling cl
Hey now, its the other way around. Using too much automated VS-Code stuff makes me confused as to which .json /.yaml file is causing the Code-extension for CMake to malfunction and what is actually being passed to the the compiler.