Modifying elemvariables.cmake to account for the case where there are no MPI include flags.
Modifying elemvariables.cmake to account for the case where there are no MPI include flags.

justusc/Elemental,sg0/Elemental,justusc/Elemental,mcopik/Elemental,justusc/Elemental,birm/Elemental,mcopik/Elemental,birm/Elemental,justusc/Elemental,justusc/Elemental,sg0/Elemental,sg0/Elemental,birm/Elemental,sg0/Elemental,birm/Elemental,sg0/Elemental,birm/Elemental,sg0/Elemental,mcopik/Elemental,justusc/Elemental,mcopik/Elemental,mcopik/Elemental,mcopik/Elemental,birm/Elemental