Ah... bei tempi quando l'Amiga aveva la sua bella RAM Disk di default... 
...The bottleneck in my situation is definitely disk I/O - building a solution results in plenty of reads and even more writes. The logical choice would be buying WD Raptor disks that spin at 10,000rpm. It should reduce build times somehow. However, there is another solution that reduces build times dramatically. Literally.
It is called RAM disk. Instead of working with files residing on physically disk, you work with files residing in RAM...