升级到最新的mac os Mavericks。装json出现错误：
代码如下:
gem install json -v ‘1.8.1’
Building native extensions. This could take a while…
ERROR: Error installing json:
ERROR: Failed to build gem native extension.
/usr/local/var/rbenv/versions/2.0.0-p247/bin/ruby extconf.rb
creating Makefile
make “DESTDIR=”
