added info in makefile

config_files/skeleton_makefile

@@ -85,6 +85,8 @@ all: $(NAME)
 #  - and directory "$(D_OBJS)" is order-only prerequisite :                        
 #    - it must exist before executing rule                                         
 #    - but last time modification is not checked
+#    - it avoids recompiling each time because the build folder was
+#      modified by creation of other objects files
 $(D_OBJS)/%.o: %.$(EXT) | $(D_OBJS)
 	@echo $(CYAN)"compilation (objects.o) :"$(RESET)
 	$(CC) $(CFLAGS) -c $< -o $@