FPC is in $PATH after installing Lazarus 2.2, right? In your GitLab main directory run "make clean all" or "make clean bigide". Then start Lazarus.exe from the cmd line.
Build it again from Lazarus Tools menu with all the debug flags. There is a "Debug IDE" profile to choose.
You can choose more packages to install before building.
Don't copy any directories from the 2.2 release.