CMake: Add ENABLE_FUZZING and "afl" target

fuzzing/CMakeLists.txt

@@ -0,0 +1,21 @@
+option(ENABLE_FUZZING "Create executables and targets for fuzzing cJSON with afl." Off)
+if (ENABLE_FUZZING)
+    find_program(AFL_FUZZ afl-fuzz)
+    if ("${AFL_FUZZ}" MATCHES "AFL_FUZZ-NOTFOUND")
+        message(FATAL_ERROR "Couldn't find afl-fuzz.")
+    endif()
+
+
+    add_executable(afl-main afl.c)
+    target_link_libraries(afl-main "${CJSON_LIB}")
+
+    if (NOT ENABLE_SANITIZERS)
+        message(FATAL_ERROR "Enable sanitizers with -DENABLE_SANITIZERS=On to do fuzzing.")
+    endif()
+
+    add_custom_target(afl
+        COMMAND "${AFL_FUZZ}" -i "${CMAKE_CURRENT_SOURCE_DIR}/inputs" -o "${CMAKE_CURRENT_BINARY_DIR}/findings" -x "${CMAKE_CURRENT_SOURCE_DIR}/json.dict" -- "${CMAKE_CURRENT_BINARY_DIR}/afl-main" "@@"
+        DEPENDS afl-main)
+
+
+endif()