I have to check, but IIRC on IOS there is some tricky business. The actual exe should be inside the bundle.
It may be that the IDE creates it outside and sets a symlink in the bundle, not sure gdb deals with this. Maybe if you change the project settings to have the exe put directly into the bundle.
Sorry that is not very specific, but its a long time I looked at a Mac.
Another thing could be dwarf vs stabs (mind that needs to be set for each package). But I am not sure that would cause the error you got.