Remove unnecessary CMAKE_FORTRAN_COMPILER definition from CMakeList.txt

[chan-hoo]

To resolve the issue #48, the dummy definition CMAKE_FORTRAN_COMPILER is removed from CMakeLists.txt.
Without it, nexus is compiled successfully on Hera, Orion, Hercules, and Derecho.

[zmoon]

I agree that CMAKE_Fortran_COMPILER env/shell variable should not be required, though I would think you would generally want to set it anyway (or FC) for clarity and to be sure the correct compiler is used.

[chan-hoo]

Yes, it is defined in the build module file for other machines, but Derecho doesn't want it.

[zmoon]

Derecho doesn't want it

Interesting, do they say why?

[chan-hoo]

Derecho doesn't want it

Interesting, do they say why?

I am reading through the docs. I'll let you know if I find it.