If a build is run because of a change in the source code (SCMTrigger) all variables are empty.

We have a deployment pipeline that builds a war file and deploys it on to a development environment.
In order to know who is responsible for the current status on this development environment we want to write the username into a file that is contained in the war file.
This works when the build is run manually but not if it is run from the SCMTrigger.