Currently, via a BuildWrapper, I can add additional env variables to a running
build. However, those variables do not persist past the execution of the actual
core build steps. This means that they are not available to post build steps
(e.g. Publishers).

In my context, I want to be able to set a custom version string that is used
both by the ant builder when generating my build artifact(i.e. version string in
the jar manifest) and refer to that same version string in the svn tag publisher
so it is used as the svn tag for the build.

I'd very much like to have support for setting custom env variables that are
visible throughout the build execution.