Both ubusd and cli TARGET_LINK_LIBRARIES reference ${json} which is
obtained via find_library(), but since the find_library() is searched
after the TARGET_LINK_LIBRARIES for ubusd, ubusd always gets an empty
${json} variable.
examples/server also links against libjson-c, but we were not setting
TARGET_LINK_LIBRARIES accordingly, so do that too with ${json} appended.
This was causing linking errors for ubusd and then examples/server using
an external toolchain (stbgcc-4.8-1.x).
Fixes: 9f52d1769b ("cli: use the new json-c library name")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
053be7df87