cmake HB_HAVE_CAIRO examples

RavEngine/RavEngine deps/harfbuzz/CMakeLists.txt :25 

option(HB_HAVE_CAIRO "Enable cairo interop helpers" OFF)

RavEngine/RavEngine deps/harfbuzz/CMakeLists.txt :369 

message(FATAL_ERROR "HB_HAVE_CAIRO is ON but Cairo libraries are not found")