UNIX网络编程编译出错：Undefined symbols for architecture x86_64:

我最近开始学UNIX网络编程（第三版），在配置好以后，编译/intro/daytimetcpcli.c文件时出了问题
问题如下：

gcc -I../lib -g -O2 -D_REENTRANT -Wall   -c -o daytimetcpcli.o daytimetcpcli.c
gcc -I../lib -g -O2 -D_REENTRANT -Wall -o daytimetcpcli daytimetcpcli.o ../libunp.a -lresolv -lpthread
ld: warning: ignoring file ../libunp.a, file was built for archive which is not the architecture being linked (x86_64): ../libunp.a
Undefined symbols for architecture x86_64:
  "_err_quit", referenced from:
      _main in daytimetcpcli.o
  "_err_sys", referenced from:
      _main in daytimetcpcli.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [daytimetcpcli] Error 1

我的系统是macOS10.13.6，gcc信息如下

Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.4)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

我到网上找到的解决办法都是使用Xcode更改BuildSetting，但是我之前由于电脑空间不够把Xcode删了，所以现在想问问有没有不用下载会Xcode就能解决的办法，实在不行我就只有下回Xcode了

望各位大佬解答，非常感谢

libunp.a重新在当前机器上编译一次