build: create copy of kernel binary with debug symbols

Makefile

@@ -53,6 +53,8 @@ $(BUILD_DIR)/$(KERNEL_EXEC): $(ALL_KERNEL_OBJECT_FILES)
 	@printf "    \033[1;36mLD\033[0m     \033[1mbuild/\033[35m$(KERNEL_EXEC)\033[0m\n"
 	@mkdir -p $(@D)
 	@$(LD) $^ -o $@ $(LDFLAGS) $(ARCH_LDFLAGS)
+	@cp $@ $@.dbg
+	@$(STRIP) $@
 
 $(BUILD_DIR)/%.o: %.S
 	@printf "    \033[1;32mAS\033[0m     \033[35m$(KERNEL_EXEC)\033[0m/$<\n"