CMake - adding a build step using pre-processed source files

[ukmo-ccbunney]

Hi all,
We are looking to use a build tool called Psyclone that will process source code files and generate extra code (specifically around enabling parallelization).

This tool reads the pre-processed source files (i.e. the output from cpp/fpp that can be generated as an intermediate file by the compiler) and will output a new source file for the compiler to compile.

My question is: does anyone know how to insert an extra build step like this into the CMake build system?
Essentially we need to intercept the pre-processed source files in the build step and pass a modified file to the compiler.

Thanks.