[CMake] Using m4 as a additional preprocessor for C/C++

[Denis Scherbakov]

> Is it possible to set the preprocessing to all .m4 files
> avoiding a
> manual specification of list of files to processed?

I don't know of such, but it does not mean that it does not exist.

If your list of files changes all the time, you can use FILE(GLOB...)
to find all *.m4 files to automate process.

(Please also not that somebody submitted a hint that COMMAND m4 ARGS ... > ... may actually work,
the trick is COMMAND and ARGS. But I did not try it.)

Denis