[CMake] How to assign version numbers from a source header to CMake variables?

[SF Markus Elfring]

> I use a simple text file with the build number, which is tracked under
> VCS. During the build I parse it, generate my version header, increase
> the number, save it to the file and check it in.

Which (CMake) commands do you use for this approach?

Regards,
Markus