尝试安装时出现以下webdriver gem错误Cygwin：
“gem install selenium-webdriver-2.26.0.gem”：（注意我想在 Cygwin 下使用 Ruby 安装 Webdriver gem）。
$ gem install selenium-webdriver-2.26.0.gem
Building native extensions. This could take a while...
ERROR: Error installing selenium-webdriver-2.26.0.gem:
ERROR: Failed to build gem native extension.
/usr/bin/ruby.exe extconf.rb checking for ffi.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/bin/ruby
--with-ffi_c-dir
--without-ffi_c-dir
--with-ffi_c-include
--without-ffi_c-include=${ffi_c-dir}/include
--with-ffi_c-lib
--without-ffi_c-lib=${ffi_c-dir}/lib
--with-libffi-config
--without-libffi-config
--with-pkg-config
--without-pkg-config
/usr/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/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
from /usr/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header'
from /usr/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
from /usr/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
from /usr/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from /usr/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from /usr/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from /usr/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
from extconf.rb:14:in `<main>'
Gem files will remain installed in
/usr/lib/ruby/gems/1.9.1/gems/ffi-1.2.0 for inspection. Results
logged to
/usr/lib/ruby/gems/1.9.1/gems/ffi-1.2.0/ext/ffi_c/gem_make.out
请指导我我需要做些什么来解决这个问题？任何帮助深表感谢。