I can't build firefox, because after build is almost done, there is a step where it configures firefox and needs to open a browser interface. I traced the error to:
Well, it's not an error really, since I "su -l" to get root and start the build that way. A GUI launch request from root, no matter what the app is, gets halted - as it should. What is to be done about this situation?
Code:
Error: couldn't open display (null)