Watir WebDriverのインストールに失敗する

bundle installするときにエラーとなった。

...
Installing ffi (1.9.3) 
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/bin/ruby extconf.rb 
checking for ffi.h... no
checking for ffi.h in /usr/local/include,/usr/include/ffi... no
checking for rb_thread_blocking_region()... yes
checking for rb_thread_call_with_gvl()... yes
checking for rb_thread_call_without_gvl()... yes
checking for ffi_prep_cif_var()... no
creating extconf.h
creating Makefile

make
Configuring libffi
cd "/Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3/ext/ffi_c/libffi-x86_64-darwin11.4.2" && /Applications/Xcode 5.app/Contents/Developer/usr/bin/make

/bin/sh: /Applications/Xcode: No such file or directory make: *** ["/Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3/ext/ffi_c/libffi-x86_64-darwin11.4.2"/.libs/libffi_convenience.a] Error 127

Gem files will remain installed in /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3 for     inspection.
Results logged to /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3/ext/ffi_c/gem_make.out

An error occurred while installing ffi (1.9.3), and Bundler cannot continue.
Make sure that `gem install ffi -v '1.9.3'` succeeds before bundling.

make のパスに空白が入っているのがダメとのこと。XCodeのフォルダをリネームした。

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/bin/ruby 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=/Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/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
/Users/h_yamaguchi/.rbenv/versions/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 /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
    from /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
    from extconf.rb:16:in `<main>'


Gem files will remain installed in /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3 for inspection.
Results logged to /Users/h_yamaguchi/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/ffi-1.9.3/ext/ffi_c/gem_make.out

わからん。。。こういう時は信頼と実績のStackOverflow

http://stackoverflow.com/questions/17775115/cant-setup-ruby-environment-installing-fii-gem-error