set(CUSTOM_DOCDIR "" CACHE STRING "Directory to install documentation into")
if(NOT CUSTOM_DOCDIR STREQUAL "")
set(DOCDIR "${CUSTOM_DOCDIR}")
set(CUSTOM_DOCDIR "" CACHE STRING "Directory to install documentation into")
if(NOT CUSTOM_DOCDIR STREQUAL "")
set(DOCDIR "${CUSTOM_DOCDIR}")