Instruments is able to properly symbolize my app's main bundle (as well as frameworks and libraries) in the stack trace of the extended detail view. However, symbols aren't resolved for plugins loaded during execution.
Setting the build directory where the dSym files for the main and plugin bundles are located (as well as the app itself) in the "File > Re-Symbolicate Document" menu item made no discernible difference in the stack trace.
What must I do for Instruments to load symbols for the plugins?