Which RaspberryPi? 1? maybe, 3? not an issue.....On an RPi3.
It is Raspberry Pi 3 and it is an issue. Building takes about 2 minutes on average. It may not be CPU but microsd card. I am trying fast USB (directly booting and using). Seems better. Still building takes time.
The class of SD card does not matter too much.
Lazarus itself build takes 2 minutes indeed (but also on my daughters Intel 64 laptops)
FPC takes closer to 5-7 minutes on a RPi3/Raspbian Jessie. Also note that
Raspbian is much, much faster than any other distribution.
What you can do is create a swap file of 1 Gig. That helps.
Both are very complex programs, so that is to be expected.
If your own programs take longer than seconds there is indeed something wrong.
How long takes a Lazarus rebuild on yours?
Best way to time is actually do a build from the command line and write a little shellscript...
That way you exclude Lazarus overhead.