People doing development on Bro may want to look into installing ccache. I can do a build after "make clean" in 22 seconds on my laptop now. I don't know if there is any potential to cause strange problem with ccache or not, but for the day to day builds and rebuilds it has been really nice. So far everything seems to be ok though.
It's in MacPorts too, just make sure you add /opt/local/libexec/ccache to the beginning of your PATH so that you're running it's gcc/g++ shims instead of the actual gcc and g++.