Cmake rebuilds everything when the compiler is upgraded
I'm using Debian sid. Every several days GCC is upgraded, and cmake rebuilds the entire project.
It also shows a warning for each subproject that the PCH file was created by a different executable.
I can't find a reason to rebuild everything, at least when the compiler is at the same major version (9.x). I'd understand this behavior when upgrading to a new version (10.x).
I suppose the rebuild is done because system headers are all touched. Qmake for instance ignores header changes in system include paths (all the directories that are included by the compiler, and also those included with -isystem).