The cmake logic is wrong (E.G. PKG_CHECK_FOR_MODULES fails unless all
modules are found), and the legacy libjson.so name is also used by the other
libjson (http://sourceforge.net/projects/libjson/) which provides an
incompatible API, so just drop it.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>