The use of CMake in a C++ project if used correctly can allow the programmer to focus less on the platform, program version number and more on the actual program itself. With CMake you can define preprocessor tags that allow for easy checking of which platform or any other preprocessor tags you might need in the actual program. Such as the version number which could be leveraged in a log system.
It is important to understand not every preprocessor should be defined in the
config.h.in. Preprocessor tags are generally used only to make the programmers life easier and should be used with discretion. You should research if a preprocessor tag already exists before defining it as you may run into undefined behavior on different system.