Summary
Previously, you were not breaking apart projects, but now you are enabling that feature. However, your build is still very serialized on the project level. This may also happen when you dramatically change the structure of your makefiles tree.
Solution
Run a complete fresh build with --emake-history=create. After that, remove that option again and use the new history file going forward.
This article is part of our Knowledge Base and is provided for guidance-based purposes only. The solutions or workarounds described here are not officially supported by CloudBees and may not be applicable in all environments. Use at your own discretion, and test changes in a safe environment before applying them to production systems.