Background is in this mail (and the bug report): http://mail.openjdk.java.net/pipermail/build-dev/2013-April/008772.html
In short, build time is shortened considerably both with an empty and a perfect cache when ccache is in use.
Note that this only affects full builds from the root repo and not hotspot only builds.
http://cr.openjdk.java.net/~erikj/8014074/webrev.root.01/ /Erik
