As documented in FindQJSON.cmake.
Thanks to crobi to point this out in issue 2.
#add_app_icon(qapitrace_SRCS ../icons/hi*-qapitrace.png)
link_directories(${LINK_DIRECTORIES} ${QJSON_LIBRARY_DIRS})
-include_directories(${QT_INCLUDES} ${QJSON_INCLUDE_DIRS} ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/..)
+include_directories(${QT_INCLUDES} ${QJSON_INCLUDE_DIR} ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/..)
add_definitions(-DBUILD_DIR="${CMAKE_BINARY_DIR}")