当我们在基于Debian的系统上安装ruby-debug-base的时候，有时候会遇到一下错误：
Building native extensions. This could take a while...
ERROR: While executing gem ... (Gem::Installer::ExtensionBuildError)
ERROR: Failed to build gem native extension.
ruby extconf.rb install -r ruby-debug-base
extconf.rb:1:in `require': no such file to load -- mkmf (LoadError)
from extconf.rb:1
如果出现以上问题了，请安装ruby-dev，到apt里去找可以找到。安装完后就不会报错了。
