例如：
Package opencv was not found in the pkg-config search path.
Perhaps you should add the directory containing `opencv.pc‘
to the PKG_CONFIG_PATH environment variable
No package ‘opencv‘ found
设置环境变量PKG_CONFIG_PATH方法举例如下：
找到 opencv.pc所在文件夹 比如 /test/
设置为环境变量
export PKG_CONFIG_PATH=/test/:$PKG_CONFIG_PATH
pkg-config 路径问题
原文：http://www.cnblogs.com/xuanliwei/p/4623903.html
