../../build_mouse-n_debug_nrf52840dk/mouse-n/nrf_log_frontend.c.o
../../build_mouse-n_debug_nrf52840dk/mouse-n/nrf_log_str_formatter.c.o
</code>    

When make is used with parallelism enabled stdout is not
synchronised by default. So some output from previous make target is catched by above
macro which cause linker to show error.
Additional lines looks like:
<file txt mouse-n.in>
make[1]: Entering directory
../../build_mouse-n_debug_nrf52840dk/mouse-n/nrf_log_frontend.c.o
../../build_mouse-n_debug_nrf52840dk/mouse-n/nrf_log_str_formatter.c.o