port upgrade outdated fails

[Chris Jones]

>> Do what it says. Install arpack and mpich-default with the same fortran variants.
>>
>> Most probably you have mpich-default installed with the older gcc8 variant active, so just uninstall it and then reinstall with the new default, which is gcc9.
>>
>> Chris
> 
> It’s not that simple, there are several dependent ports that were built to the gcc8 variant. Why did the default gcc change in the first place?

gcc9 default the default when it was release, last year.

Its up to you what you do here. either use gcc8, or gcc9. not a mixture 
of both.

Chris