I am stuck in an environment with CMake, GCC and Unix Make (no clang, no ninja) and getting detailed information about WHY the build is taking so long is nearly impossible.

I have a similar problem, with a tangential question that I think about from time to time without really having the time to investigate it further, unfortunately.

I notice sometimes that CMake recompiles files that shouldn't have been affected by the code changes made previously. Like recompiling some independent objects after only slight changes to a .cpp file without any interface changes.

So I often wonder if CMake is not making some file more inter-dependent than what they are, leading to longer compilation times.