Update README.md

packages for gdb 32bit program in 64 bit linux system

README.md

@@ -88,7 +88,7 @@ ucore OS实验了。
 ```
   $ sudo apt-get update
   $ sudo apt-get upgrade
-  $ sudo apt-get install build-essential git qemu-system-x86 vim-gnome gdb cgdb eclipse-cdt make diffutils exuberant-ctags tmux openssh-server cscope meld
+  $ sudo apt-get install build-essential git qemu-system-x86 vim-gnome gdb cgdb eclipse-cdt make diffutils exuberant-ctags tmux openssh-server cscope meld gcc-multilib g++-multilib
 ```
 [NOTICE] 最小需要的安装包： build-essential git qemu-system-x86 gdb make diffutils