Added udunits-2.2.26

# Installation instructions

## Prerequisites

You need to have libexpat installed in `$EXPAT_DIR`. See [UDUNITS documentation](https://www.unidata.ucar.edu/software/udunits/udunits-current/doc/udunits/udunits2.html#Prerequisites) for details.

## Download Source

First download the source into directory `$DIR` (placeholder for the directory of your choice).

```bash

cd $DIR

wget wget ftp://ftp.unidata.ucar.edu/pub/udunits/udunits-2.2.26.tar.gz

tar -xzf udunits-2.2.26.tar.gz

# Fix autoconf scripts for SX AURORA

cd udunits-2.2.26/build-aux

rm config.sub config.guess

wget \

https://raw.githubusercontent.com/SX-Aurora/autoconf-helper/master/config.guess \

https://raw.githubusercontent.com/SX-Aurora/autoconf-helper/master/config.sub

```

## Build and install

On the front-end, we can cross-compile. Remember to replace `$PREFIX` with your installation directory.

```bash

cd $DIR/udunits-2.2.26

# configure the package

./configure \

CC=ncc CXX=nc++ FC=nfort F90=nfort LD=nld AR=nar RANLIB=nranlib \

CFLAGS=-O3 CPPFLAGS=-I$EXPAT_DIR/include LDFLAGS=-L$EXPAT_DIR/lib \

--host=ve-nec-linux-gnu --prefix=$PREFIX

# build

make

# test

qlogin -q veinteractive -l elapstim_req=1800

cd $PBS_O_WORKDIR

make check

exit

# install

make install

```