opened a terminal and typed:
$ sudo lazarus-ide
I added lazreports and weblaz and then did the rebuild, now everything's working.
The idea was to do it without sudo. Can you please try again as a normal user. Just don't touch "Clean All". Maybe delete ~/.lazarus again before testing. It seems only you still have this problem. Rails confirmed that only "Clean All" causes problems for him. Maybe some old versions had more problems, I don't know, but now we test 1.2RC2.
AFAIC it's no big deal, in fact it's sensible that if I installed it with sudo I should have to rebuild it with sudo. I think a simple reminder note on the rebuild screen should suffice, just to stop melons like me tripping themselves up.
No, it is important that you can install packages without sudo rights.
Lazarus does not support dynamic packages now, but installing static packages is almost as easy from Package -> Install/Uninstall packages ...
You don't need to think of it, you just install by clicking a button.
Things would be much worse if you had to quit Lazarus, run it as sudo, install a package, quit it again and then start it again as normal user.