[mpich-discuss] How to spawn a non-MPI process with MPI_Comm_spawn

I'm attempting to use MPICH to manage a number of non-MPI processes. The latter call system() and fork(), which as I understand it may cause undefined behavior if they were spawned as MPI processes. How do I use MPI_Comm_spawn() to launch these processes? For example, OpenMpi has a key for the "info" field named "ompi_non_mpi", which causes a non-MPI process to be spawned. Is there something similar in MPICH? Thanks, Kurt