See the developer information wiki page for more information:
https://wiki.eclipse.org/UPR_Developer_Info
UPR is build using Tycho, so Maven 3 has to be installed. The main build script for the standardized profiles is located in project "standardized/build/org.eclipse.upr.build". Execute e.g. "mvn clean install" in that directory to build all projects.
The UPR update site will be available in directory "standardized/build/org.eclipse.upr.profiles/target" after a successful build.
Gitlab Project Group
You can use the code from these repositories to experiment, test, build, create patches, issue pull requests, etc.
eclipse/upr - Project group hosted on The Eclipse Foundation's GitLab instance.