If your development machines don’t have solid state drives (SSDs): go buy some.
If your continous integration (build) box doesn’t have a solid state drive: go buy one.
Solid state drives are the quickest and cheapest way to speed software development. As most continuous integrations/builds are IO, solid state drives provide tremendous speed increases: I’ve seen builds and tests run in less than a fifth of the time a traditional moving hard disk would take. Solid state drives have reached a price point where the lower capacity ones are on par with higher capacity hard disks (which you don’t need unless you’re storing movies etc.)
It used to be that the build machine would use some crappy hardware lying around: often an old development machine someone no longer used. This is one of the worst decisions you can make on a project.
Having a super fast SSD based build machine will ensure fast, reliable build results, fast feedback and a happy development team.