cmake HEXL examples

IntelLabs/hexl example/cmake/CMakeLists.txt :9 

find_package(HEXL 1.2.6
    HINTS ${HEXL_HINT_DIR}
    REQUIRED)

zju-abclab/NEXUS thirdparty/SEAL-4.1-bs/CMakeLists.txt :226 

find_package(HEXL 1.2.4)