我有Compass的问题，当我想安装它时，我有此消息错误
sh-3.2# gem install compass --source http://rubygems.org
Building native extensions. This could take a while...
ERROR: Error installing compass:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -r ./siteconf20160524-691-6ackvr-0.rb extconf.rb
mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/ffi-1.9.10 for inspection.
Results logged to /Library/Ruby/Gems/1.8/extensions/universal-darwin-10/1.8/ffi-1.9.10/gem_make.out
安装了Ruby
sh-3.2# ruby -v
ruby 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin10.0]
操作系统版本为10.6.8