I want to add custom fields to my global listener measurement for a build.

As I understand from the Global Listener Documentation, I have the option to set the environment variables 

INFLUXDB_PLUGIN_CUSTOM_FIELDS
INFLUXDB_PLUGIN_CUSTOM_TAGS 

The note states

"The environment variables must be set on the final build object. If you are creating or updating these variables in a pipeline, you should make sure they are exported with an EnvironmentContributingAction."

I tried setting the variables in the pipeline environment, for example

pipeline {
  environment {
    INFLUXDB_PLUGIN_CUSTOM_FIELDS = "foo=bar"
  }
  ...
} 

but the data doesn't appear in my InfluxDB measurement.

I took a look into the code but I can't find a mistake there. What is the correct way to set the environment variable on the "final build object"? Could you please give an example for that?

Cheers!

Update

I even set the environment variable INFLUXDB_PLUGIN_CUSTOM_FIELDS globally for my build agent but it still isn't added to the measurement.

Update2

Setting the environment variable globally (not only for the build agent but in "Manage Jenkins") does the job. But that brings me back to the question: How can you set this variable in a pipeline? I would be very happy about an example