Xcode rebuilding whole project after reboot

I have a large C++ Xcode project with includes several dependencies and, normally, AppleClang is good at detecting changes in source files and rebuilding only affected dependencies. However, if I reboot the MBP, for some reasons at the first launch of Xcode the entire project gets rebuilt, as if all the source code got flagged as changed during reboot. Of course, no change in the source code happens during reboot, so I'm wondering what is flagging the code as "changed" during a reboot to trigger a full rebuild. Current version of Xcode is 13.2.1 (13C100), but this has been happening for years. Although this may not matter with small project, this is annoying in my case because it takes about 30 minutes to rebuild the whole project.