Where to get the org.iets3.core.expr.base build script?

While attempting to create my custom language plugin, I encounter an error stating that the org.iets3.core.expr.base module is not found. This issue arises because I have incorporated the related org.iets3.core.expr.base language as a dependency in one of my languages.

A similar situation occurs with de.itemis.mps.extensions when utilizing certain modules from that source. However, a solution exists for this problem in the form of a build plugin, which can be found here: https://plugins.jetbrains.com/plugin/17136-de-itemis-mps-extensions-build 

I am seeking information on where to obtain a comparable build plugin for the org.iets3.core.expr.base module.