我有一个新项目需要使用瘦，但是有问题。在我的 Gemfile 中。
gem 'thin'
然后我运行“捆绑安装”。表明：
......
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/local/Cellar/ruby/1.9.3-p194/bin/ruby extconf.rb
checking for main() in -lc... *** 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/Cellar/ruby/1.9.3-p194/bin/ruby
--with-thin_parser-dir
--without-thin_parser-dir
--with-thin_parser-include
--without-thin_parser-include=${thin_parser-dir}/include
--with-thin_parser-lib
--without-thin_parser-lib=${thin_parser-dir}/lib
--with-clib
--without-clib
/usr/local/Cellar/ruby/1.9.3-p194/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/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:461:in `try_link0'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:476:in `try_link'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:619:in `try_func'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:845:in `block in have_library'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:840:in `have_library'
from extconf.rb:4:in `<main>'
Gem files will remain installed in /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/gems/1.9.1/gems/thin-1.5.0 for inspection.
Results logged to /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/gems/1.9.1/gems/thin-1.5.0/ext/thin_parser/gem_make.out
An error occured while installing thin (1.5.0), and Bundler cannot continue.
Make sure that `gem install thin -v '1.5.0'` succeeds before bundling.
请帮我解决这个问题。之前安装过thin，不知道为什么这次失败了。