Adding a dll

I would like to create installers for modified builds of Mozilla and 
Firefox. No additional downloadable components will be required since 
I'm just adding svg support. I've been reading the instructions at:

http://www.mozilla.org/projects/firefox/installer/build.html
http://www.mozilla.org/projects/xpinstall/wizard/windows/
and surrounding docs

I can build by just adding the file gdiplus.dll to 
redist\microsoft\system, so to create the installer I think I just need 
to change one or more of the scripts, but I'm not sure which one(s) or 
what changes to make. Can anyone help me, or point me in the right 
direction?

-Jonathan