Whenever envvar is available on slave (either inherited from system or configured on slave), its value can not be overridden during build by envvar contributing extension points:
- possibly others
This works correctly when envinject is not installed. The culprit seems to be that EnvInjectPluginAction retains all envvars (not only those envinject contributed) early in the build and put this values back as it implements EnvironmentContributingAction. Any value that was overridden by a plugin is then reset to its original value.