我收到错误（Ubuntu 14.04）：
sudo gem install
jekyllBuilding native extensions. This could take a while...
ERROR: Error installing jekyll:
ERROR: Failed to build gem native extension.
/usr/bin/ruby2.1 extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /var/lib/gems/2.1.0/gems/ffi-1.9.14 for inspection.
Results logged to /var/lib/gems/2.1.0/extensions/x86_64-linux/2.1.0/ffi-1.9.14/gem_make.out
安装ruby-dev等常见解决方案无效。
请帮忙。谢谢。