mac os xでruggedのインストールに失敗する

エラー

$ bunlde install
...
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

checking for gmake... no
checking for make... yes
checking for cmake... yes
checking for pkg-config... no
ERROR: pkg-config is required to build Rugged.
*** 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/xxxx/.rbenv/versions/2.1.1/bin/ruby
    --use-system-libraries

extconf failed, exit code 1

解決法

homebrewでpkg-configを再インストールしてから、bundle installを再実行したら解決した

$ brew reinstall pkg-config && brew unlink pkg-config && brew link pkg-config
$ bundle install