I managed to make it work after digging a little more in the doc and source code, I share with you the working module.
This module when imported if there are any .rep files (QtRO (remote objects)) module remote object definition) in your project, it will invoke the repc compiler and compile them and put the resulting .h file in your source directory.
Still not complete, I didn't find a way to manipulate the files property of the Product Item to add the .h to it automatically.
filePath: "repc_" + FileInfo.baseName(input.fileName) + "_source.h"
var cmd = new Command();
cmd.description = "repc " + input.fileName;
cmd.program = "repc.exe"
cmd.arguments = ["-i", "rep", "-o", "source", input.filePath, output.filePath];
In order to this module to work, the repc.exe must be in your path.
Any suggestion are welcomed.