Building ImageMagick-6.8.6-8 on MacOS X 10.8.4

ImageMagick 6.8.6-8 is a pain to compile from scratch on MacOS X 10.8.4. The following notes outline the main steps I had to follow to get it to build.

The key step seems to be installing the missing pkg-config binary, pointing to the .pc files installed by XQuartz.