[CMake] Can CMake prompt the user for input while it's running?

[Naram Qashat]

I'm wondering if it's possible for CMake to prompt the user for input when it's 
running, as opposed to relying on passing in arguments for input.  Main reason 
I'm looking for something like this is so we can have optional files that can be 
enabled or disabled by the user when CMake is run.  Ideally this should be able 
to be done if a certain command-line flag is passed in.

Thanks,
Naram Qashat