When running

  $ mpif77 -c example.f -o example.f.o

mpif77 recognizes -o and produces example.f.o, but when running

  $ mpif77 -o example.f.o -c example.f

the -o option is ignored and the object file is example.o.  Performing
the same experiment on the underlying compiler tool or with the mpicc
and mpiCC wrappers does not exhibit this behavior, so the issue appears
to be specific to mpif77.

Reported-by: Zhen Wang <zwang26@emory.edu>