Fix cmake auto-installer

Commit 69e6a808 accidentally broke the feature of automatically installing cmake on the fly if it isn't present.

It's easy too fix.

TBH, I never liked this feature. It's counter-intuitive, and doesn't address the notion of dependencies in the proper way. cmake is a significant piece of software to build, and in my opinion it is better to have the users download cmake from their distribution instead of trying to compile it.