Marking BUILD_PHASTA_ADAPTOR as advanced and fixing warnings.

The other adaptors don't need the Fortran compiler even though it
is specified which gives the following warning:
CMake Warning:
  Manually-specified variables were not used by the project:

    CMAKE_Fortran_COMPILER

This change also gets rid of that warning by provided the
Fortran compiler only when needed.

Change-Id: I5424df7ed16a33fc4bf4b427ded923c1c8eb9e90
Merge topic '13997_disable_phasta_adaptor' into next

d667a67 Marking BUILD_PHASTA_ADAPTOR as advanced and fixing warnings.