cmake: don't use bundled RapidJSON with old CMake
cmake: don't use bundled RapidJSON with old CMake

add_library(INTERFACE IMPORTED) can't be used with CMake 2.8.

groonga/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,groonga/groonga