"--add-package" is to add a package to the IDE for installation, which is what you do in the IDE's "Install/Uninstall Packages" window. It allows you to simply specify the package name if it is located in the "lazarus\components" folder.
However, if it is not there, then lazbuild needs to specify the path via "--add-package-link". This will not install the package, but will only tell you where to look for it. Apparently OPM uses this to add paths to downloaded packages.
However, you can immediately specify in "--add-package" not the name, but the path to the .lpk-file.
Yes, lazarus/lazbuild has a problem with quotes in parameters in some places. I've almost written a patch to fix this.
To build "startlazarus" you can use "make starter". And instead of using "lazbuild --build-ide=" for a complete rebuild, you can use "make useride". You can find a lot of interesting information in the help of the Makefile itself: "make help" (in the lazarus directory).