In building my own QSB plugins I have just been adding my code to the main QSB xcode project. This was less than ideal, since every time a new QSB version was released my changes to the xcode project file would get wiped out. It was also a bit tricky since QSB lives in subversion and I was managing my plugins with git.
Happily, I think I’ve improved the situation a bit.
First, many thanks to Steven Noonan who set up a QSB mirror on github - I’m now able to include the QSB code base in my own plugin project via git submodules.
Next, I continued my slow learning experience with xcode and eventually figured out how to build my plugins in their own project. This is probably obvious to experience xcoders, but my eureka moment occurred when I realized you could drop other xcode project files into your own project as sub-projects. This let me add the QSB Vermilion framework from the aforementioned git submodule as a dependency of my plugins. I had a bit of trouble getting xcode to include Vermilion headers the right way - the FRAMEWORK_SEARCH_PATH trick on this page helped me through that.
So - the end result - I have an xcode project just for my plugins that should gracefully handle updates to the main QSB code base. And I learned a bit about git and xcode along the way ;-)
If you are interested you can check out the xcode project in the github repository.