I recently found out there is now a free edition of Incredibuild included in MSVC 2015 (since the autumn 2015 update 1). It’s a bit hidden away but this MS blog post describes how to download and run it inside Visual Studio:
Incredibuild is marketed as a distributed build system for Visual Studio, but it also builds much faster than the standard system on a local machine, mostly by scheduling tasks better on multiple cores. The free license works on up to 8 cores. In addition Incredibuild provides build graphs and metrics to help optimize build times.