Function nros_boot_report_note_heap 

#[unsafe(no_mangle)]
pub extern "C" fn nros_boot_report_note_heap(
    _peak: usize,
    _capacity: usize,
)

The C entry point exists in BOTH builds, unlike every other stub here.

The Rust half of an image takes the record from a cfg and the C half takes it from CONFIG_NROS_BOOT_REPORT; the two are set from the same knob and can still be built apart (a stale cargo artifact, a C smoke test). An absent symbol makes that a LINK failure naming nothing in particular, so the disabled build keeps an empty body instead.