Last time I benchmarked C++ compilation on SSDs vs HDDS (compiling the PCL project on Linux which took around 45 minutes), SSD didn't help in a noticeable fashion.
I believe that this makes sense:
In a typical C++ project like that which use template libraries like CGAL, compilation of a single file takes up to 30 seconds of CPU-only time. Even though each file (thanks to lack of sensible module system) churns through 500 MB of raw text includes, that's not a lot over 30 seconds, and the includes are usually from the same files, which means they are in the OS buffer cache anyway so they are read from RAM.
However, if the project uses C++ like C, compilation is a lot faster; e.g. for Linux kernel C builds, files can scroll by faster than a spinning disk seek time would allow.
