Can't install rmagick, pkg-config: command not found

I'm trying to install rmagick on my Mac OS X v10.9 (Mavericks) machine. However. I get this error ``` /usr/local/bin/Magick-config: line 41: pkg-config: command not found /usr/local/bin/Magick-config: line 47: pkg-config: command not found /usr/local/bin/Magick-config: line 50: pkg-config: command not found /usr/local/bin/Magick-config: line 53: pkg-config: command not found checking for stdint.h... yes checking for sys/types.h... yes checking for wand/MagickWand.h... yes /usr/local/bin/Magick-config: line 53: pkg-config: command not found Can't install RMagick 2.13.2. Can't find the ImageMagick library or one of the dependent libraries. Check the mkmf.log file for more detailed information. ``` The lines 41,17,50,53 in Magick-config are ``` --cflags) pkg-config --cflags MagickCore ;; --cxxflags) pkg-config --cflags MagickCore ;; --cppflags) pkg-config --cflags MagickCore ;; --ldflags) pkg-config --libs MagickCore ;; --libs) pkg-config --libs MagickCore ;; ``` I installed ImageMagick with `brew install imagemagick --build-from-source` and before running `gem install rmagick`, I set the path to MagickCore.pc with `export PKG_CONFIG_PATH=/usr/local/Cellar/imagemagick/6.8.9-1/lib/pkgconfig` and the path to Wand.h with `export C_INCLUDE_PATH=/usr/local/Cellar/imagemagick/6.8.9-1/include/ImageMagick-6/`. This worked for the Wand, but not for MagickCore, as I still get `pkg-config: command not found`. I use Ruby 1.9.3p545 and Ruby on Rails 3.2.16. How can I fix this problem?