unset CONFIG_SITE
remove explicit configure option --libdir

Unsetting CONFIG_SITE was the right way to solve the problem that
--libdir was working around.

This reverts commit 0b3240f9d8c74205cf128e9a7f865f22dbd6e771.
This reverts commit 3653eb6ec1ba0f178e4ab39d7e9b72acb36298e9.
This reverts commit 593ab5a7068d6142903ab839237100e92a5071f3.