cice5: use ifort -cpp instead of cpp for preprocessing

[anton-seaice]

In the cice4 and cice5 builds, the CPP directive __INTEL_COMPILER is not defined. Having this defined in the code would allow for clearer handling of errors (e.g. #48 (comment))

@blimlim identified this is because the preprocessor directions are processed using CPP instead of an intel compiler.

@manodeep suggests using ifort -cpp instead for preprocessor handling

I have tested this and when using ifort -cpp then __INTEL_COMPILER is defined

[anton-seaice]

Leaving this open in the hope I revisit for master branch, and make the same change there.

[anton-seaice]

In #52 - the fix only work for intel compilers.

Intel needs:

-fpp -P

And gfortan needs

-cpp -E