[CMake] File modification detection based on content (not timestamp)

[John Drescher]

> ### QUESTIONS ###
> 1. Is file modification detection based on file content instead of
> timestamp supported already?
> 2. Is support for it planned?
> If not, i would like to make a feature request!
> 3. How hard would it be to implement that?
>
I could be totally wrong but doesn't CMake have nothing to do with
this? I mean CMake generates Visual Studio Projects, unix makefiles
... and its up to whatever build system you use to handle its
dependencies how correctly.

John