[berkut]

I guess it depends on how you define "very little", and what system includes you have.

I've just tested one of my ~300 KLOC C++ projects, broken into 479 .cpp files and 583 .h files.

Using Linux (GCC) after dropping the disk cache, on a 5400 RPM HD, the full build on 14 threads took: 78 seconds.

On a fast SSD (same machine, after dropping caches again) it took 61 seconds.

Linking was ~7 seconds faster on the SSD, so arguably you could say that actual compilation wasn't the same ratio as fast, but overall build time is most definitely faster.

Source was on the same drive as the build target directory.

At a previous company I worked at, we got SSDs to speed up compilation (and it did).