Icecream is a distributed compile system. It allows parallel compiling by
distributing the compile jobs to several nodes of a compile network running the
icecc daemon. The icecc scheduler routes the jobs and provides status and
statistics information to the icecc monitor. Each compile node can accept one
or more compile jobs depending on the number of processors and the settings of
the daemon. Link jobs and other jobs which cannot be distributed are executed
locally on the node where the compilation is started.
Note that upon installation of the resulting package, all your software
will be compiled by icecream by default.

For information on how to use icecream in combination with ccache see
https://github.com/icecc/icecream#how-to-combine-icecream-with-ccache

librsync is an optional dependency.