[CMake] Pure Python project

[Emmanuel Blot]

> The command
>   add_custom_command(OUTPUT myout.txt COMMAND ...)
> tells CMake how to generate myout.txt.  Then you have to tell CMake  
> you
> want to generate it by depending on the output from a target.  The
> target can either be an executable you're already building:
>  add_custom_target(MyDriverTarget ALL DEPENDS myout.txt)
> The "ALL" option makes the custom target build by default.
>
> -Brad

Thanks Brad, it works perfectly.
Thanks also for the clarification about ADD_CUSTOM_TARGET vs.  
ADD_CUSTOM_TARGET, I got lost.

Cheers,
Manu