Docs: Extend Incompatibilities section of cmake documentation

This MR extends the Incompatibilities section of cmake documentation, specifically on mac-specific builds, and on compilation failure due to dangling autotools files.

I would also be tempted to add a sentence on LibXC:

One can get a compilation error with LibXC, where libxc is detectable in the $PATH (i.e. installed with a package manager) but its f03 interfaces are not correctly exposed. This is a packaging problem, and the solution is to have cmake fetch the correct version, rather than use the packaged version.

if you think this makes sense.