A) Install MPI.
Make sure that the mpi compilers (mpicc?) are in the path visible to SCons; if they don’t install to the standard place that the normal user can see, then you can try going into rosetta_source/tools/build and copying the file “site.settings.topsail” to the file “site.settings”; this causes SCons to look in more places for compilers.
C) add “extras=mpi” to your compile command line.