cmake OC_HAVE_FLOAT16 examples

iotivity/iotivity-lite CMakeLists.txt :969 

try_compile(OC_HAVE_FLOAT16 ${CMAKE_BINARY_DIR} ${PROJECT_SOURCE_DIR}/tools/test_float16.cpp)

iotivity/iotivity-lite CMakeLists.txt :972 

list(APPEND TEST_COMPILE_DEFINITIONS "OC_HAVE_FLOAT16")