As far as I understand GPL, it uses the author's copyright to restrict usages of their code: Whenever someone wants to use this piece of code, he also has to publish his modifications if he distributes the resulting executable. Local modifications for your own use do not require public disclosure.
According to here, cmake works like gcc, where CmakeLists.txt ist the source code and the resulting Makefile is the resulting binary.
To my knowledge, this renders GPL on CmakeLists useless. Anyone can use CMakeLists licensed under GPL for their own project, as they will never share the resulting Makefile. Additionally, the Makefile does not contribute to the final binary the same way that my editor's programmer doesn't get to claim copyright on every piece of code I write in this editor, so the project does not need to be under GPL itself.
Surely, this is no fundamental problem: I do have the copyright for my own CMakeLists. I could come up with a new Licence, the Berne-Licence, where I state that my CMake script may only be used for GPL-Licenced Code. Is there any licence out there to fit my needs? Is there any reason why I shouldn't do that, for example compatibility reasons?
Also please feel free to correct me if some of my assumptions or conclusions are simply wrong. I have very limited experience in the copyleft / opensource ecosystem.