Welcome to Swym. This programming language is designed to let you Say What You Mean, as clearly and elegantly as possible. (It's pronounced "swim", in case you were wondering.)
This can be done via EnvInject plugin in the following way:
Create an "Execute shell" build step that runs:
echo AOEU=$(echo aoeu) > propsfile
Create an Inject environment variables build step and set "Properties File Path" to 'propsfile'.
S. Roberts, D. Howard, and J. Koza. 2001 Genetic and Evolutionary Computation Conference
Late Breaking Papers, page 359--365. San Francisco, California, USA, (9-11 July 2001)