Parallel Incremental Builds Not Working Across Projects in Xcode

[chiragramani]

We are experiencing an issue where incremental builds in a multi-project setup within Xcode run serially instead of in parallel. While we do see parallel builds for targets within the same workspace, projects with dependencies across different Xcode projects only build serially.

Repro: https://github.com/chiragramani/Xcode-Serial-Incremental-Builds

Is this a known limitation of Xcode's build system, or is there a possible fix/workaround to enable proper parallel incremental builds across multiple projects? (like some shared build configuration etc) Any insights would be greatly appreciated!