unix/Makefile: Add back LIB_SRC_C to list of object files.

This fixes the dev build (it needs LIB_SRC_C for Bluetooth) which was
broken by 136369d72f.

Signed-off-by: Damien George <damien@micropython.org>

ports/unix/Makefile

@@ -255,6 +255,7 @@ OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_CXX:.cpp=.o))
 OBJ += $(addprefix $(BUILD)/, $(SHARED_SRC_C:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(EXTMOD_SRC_C:.c=.o))
+OBJ += $(addprefix $(BUILD)/, $(LIB_SRC_C:.c=.o))
 
 # List of sources for qstr extraction
 SRC_QSTR += $(SRC_C) $(SRC_CXX) $(SHARED_SRC_C) $(EXTMOD_SRC_C)