clion still needs a cmakelists.txt that's good enough to index the project, but it doesn't have to produce a usable artifact -- you can still build with make or whatever else you want. Probably cold comfort if you use a lot of third-party libraries, but otherwise it's a fairly set-and-forget kind of thing.
I previously saw in their release notes that Makefile-based projects were out, but while digging up supporting links it seems their project formats list has gotten quite sizeable https://www.jetbrains.com/help/clion/project-models.html
It has been a while since I last used CLion. I got Nethack working with it (I did have to run it through cproto first) and at the time it auto-generated a broken cmakelists.txt that I simplified with an even more broken one that slurped up every single source file with a couple wildcards. Couldn't build that way of course, but it was enough to index all the things while the makefile did the real job. Good to know that's not a necessary step anymore.
