I wasted way to much time figuring this one out (and after I did find the problem, I realized I had run into this about a year ago in another project :-S)
In my project I'm building the various subsystems as static libraries (.a files) that get linked into a final firmware.
Unfortunately, the placement of data into custom linker sections (for `.sdh_ble_observers`, `.sdh_stack_observers.`, `.sdh_state_observers`, etc.) doesn't seem to work properly when the contents are coming from an .a file. They end up getting stripped if when their contents come from an .a file.
The easy work-around is to not bundle the .o object files into a .a file, but just link the .o files into the final firmware directly.
Anyway, I'm posting this here for my future self or for anyone else running into this problem.
