我尝试将独角兽Gem添加到我的Gem文件中，当我运行bundle install时，出现以下错误：
Installing kgio (2.8.1) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby extconf.rb
checking for CLOCK_MONOTONIC in time.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby
/usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:491:in `block in try_compile'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:443:in `with_werror'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:491:in `try_compile'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:686:in `macro_defined?'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:822:in `block in have_macro'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:821:in `have_macro'
from extconf.rb:5:in `<main>'
Gem files will remain installed in /usr/local/rvm/gems/ruby-1.9.3-p392/gems/kgio-2.8.1 for inspection.
Results logged to /usr/local/rvm/gems/ruby-1.9.3-p392/gems/kgio-2.8.1/ext/kgio/gem_make.out
An error occurred while installing kgio (2.8.1), and Bundler cannot continue.
Make sure that `gem install kgio -v '2.8.1'` succeeds before bundling.
在包含unicorn gem之前，我运行bundle install没有任何问题。看起来在尝试安装kgio 2.8.1时失败了。我在Stackoverflow和其他地方搜索解决方案，最常见的解决方案似乎是安装Xcode开发工具。我已经这样做了，但问题仍未解决。
我正在运行Mac OSX 10.9.1 Mavericks和Ruby 1.9.3p392。真的需要解决这个问题，非常感谢任何帮助。