Must use netcdf library that has been built with openmpi

Triton Install

```
git clone https://github.com/coecms/mppnccombine-fast
module load netcdf
module load cmake
cd src/mppnccombine-fast
export HDF5_ROOT=/opt/ohpc/pub/libs/gnu8/openmpi3/hdf5/1.10.5
export NETCDF_ROOT=/opt/ohpc/pub/libs/gnu8/openmpi3/netcdf/4.7.1
make
make PREFIX=/home/cermak/workdir/local install
```

Theoretical Cheyenne Install (never got working due to path issues for HDF)

```
module load netcdf-mpi
module load cmake
cd src/mppnccombine-fast
export HDF5_ROOT=/glade/u/apps/ch/opt/hdf5/1.10.1/gnu/7.1.0
export NETCDF_ROOT=/glade/u/apps/ch/opt/netcdf-mpi/4.8.1/mpt/2.22/gnu/11.1.0/
make
make PREFIX=/glade/work/jsimkins/mppnccombine-fast/ install
```

