A good solution to speed up builds on old hardware is to setup distcc to use the parallel processing power of your other CPUs.Not complicated (just cd to the directory and type 'make install clean') but on a lower end machine its going to take a long time.
I have only had success in using matching architectures for this, so for example, a G3 host can use the processing power of G4s and G5s, but not an Intel. Either way, you can turn what could be an overnight compile into a few minutes with enough POWER.
If you match the GCC version (using Tigerbrew), you should be able to theoretically use distcc on an OS X PowerPC Mac to compile for a Linux/BSD PowerPC host.
My initial reason behind researching this was to allow my 1st Gen AppleTV to use the 8 cores in my Mac Pro to compile packages under OSMC/Debian in minutes instead of days