We recently enabled GNU ccache
in the FreeCAD CMake project files on master to drastically reduce Travis build times but these changes also greatly improves local builds, especially if you tend to switch between git branches and/or rm -rf your ./build directory. To reap the benefits, you simply need to install the default ccache however if you use the CLANG compiler, instead of GCC, you should use version 3.25 or later.
On a lowly Travis dual CPU VM, a GCC build dropped from nearly an hour and 10 minutes to just over 7 minutes (10x faster) and the CLANG build dropped from nearly 48 minutes to less than 7 minutes (~7x faster). ccache performance will vary by system but I am confident local compilation will benefit even more from ccache.
GNU ccache has only been verified on Linux and macOS/OS X but it seems there are forks/patches for use with Visual Studio.
For reference here is the recent pull request
that enabled ccache. Click through if you want to see the build time benefits and additional context.