More serious - I moved to CMake presets and with that came a lot of cache optimization - including parallel builds. MacOS is now almost as fast as Windows for build, and Linux/gcc not far behind. Windows C++ seems to have the lowest modern feature compatibility, followed by MacOS/Clang, with Linux/recent GCC being the most complex. A lot of the newer features seem to add a lot to the build time..
... mind I've been working with C++ only for the last few months, and C for many years before, so consider it a beginner post in a lot of ways. Still, it was interesting to explore, and I'll be continuing to explore - I haven't yet enabled ccache for instance which I suspect will improve a lot.