nios2-app-update-makefile and long list of files

In NIOS EDS 9.1sp2, the IDE from time to time automatically performs a nios2-app-update-makefile.

In my last project, I have added lots of modules and the list of files exceeds the environment limit : getting this error message when run on the command line "The input line is too long."

Does anyone know where the routine that executes nios2-app-update-makefile is located ? I could then eventually rewrite it to perform the update in chunks (as it does not seem to accept a file as input).

Since I could not find it in the project's master makefile, I assume it must reside somewhere in the nios2eds directory. But where???

Thanks,

P9