How do I create a new XCode project for a modo plugin?
Firstly, you don't want to be creating a bundle, you want to create a C/C++ Library, set the type to Dynamic.
Then add a new target to the project, of the same type, but this one is a static library. Add the .cpp files in the SDK common directory to this target and set the header search path to look in the SDK header directory.
Then select your plugin target and go to build phases, add the SDK target as a target dependency. Also add the SDK target under Link Binary with libraries.
That should be everything you need to do.
The easiest way to see how to setup the project files is to start with the sample plugins. There are both Xcode and Visual Studio projects included.