mpich, openmpi: add gcc14 and clang18 variants

[aeiouaeiouaeiouaeiouaeiouaeiou]

Buildbots are fails to build netcdf-fortran because the requirement port does not exist.

--->  Cleaning netcdf-fortran
--->  Removing work directory for netcdf-fortran
--->  Fetching distfiles for netcdf-fortran
--->  Checksumming netcdf-fortran-4.6.1.tar.gz
netcdf-fortran +gcc12
netcdf-fortran +openmpi
netcdf-fortran +universal
netcdf-fortran +mpich
netcdf-fortran +gccdevel
netcdf-fortran +gcc13
netcdf-fortran +g95
netcdf-fortran +gcc10
netcdf-fortran +gcc11
netcdf-fortran with platform 'darwin 8 powerpc'
netcdf-fortran with platform 'darwin 8 i386'
netcdf-fortran with platform 'darwin 9 powerpc'
netcdf-fortran with platform 'darwin 9 i386'
netcdf-fortran with platform 'darwin 10 i386'
netcdf-fortran with platform 'darwin 11 i386'
netcdf-fortran with platform 'darwin 12 i386'
netcdf-fortran with platform 'darwin 13 i386'
netcdf-fortran with platform 'darwin 14 i386'
netcdf-fortran with platform 'darwin 16 i386'
netcdf-fortran with platform 'darwin 17 i386'
netcdf-fortran with platform 'darwin 18 i386'
netcdf-fortran with platform 'darwin 19 i386'
netcdf-fortran with platform 'darwin 20 arm'
netcdf-fortran with platform 'darwin 20 i386'
netcdf-fortran with platform 'darwin 21 arm'
netcdf-fortran with platform 'darwin 21 i386'
netcdf-fortran with platform 'darwin 22 arm'
netcdf-fortran with platform 'darwin 22 i386'
netcdf-fortran with platform 'darwin 23 arm'
netcdf-fortran with platform 'darwin 23 i386'
Error: No such port: openmpi-gcc14
./mpbb/mpbb: error: `mirror-distfiles' failed to run successfully