Restore compatibility with cmake 3.9 (#7329)

Restore compatibility with cmake 3.9 (#7329)

This goes back to the new cmake setup and makes it compatible again with cmake 3.9.
It mostly means we can not link object libraries and also not link other libraries to object libraries.

I've tested these changes within docker on `ubuntu:18-04` with a manually installed `cmake-3.9.6`.