cmake HAVE_CURL examples

Lewuathe/mlir-hello thirdparty/llvm-project/llvm/cmake/config-ix.cmake :234 

check_symbol_exists(curl_easy_init curl/curl.h HAVE_CURL)

root-project/root interpreter/llvm-project/llvm/cmake/config-ix.cmake :198 

check_symbol_exists(curl_easy_init curl/curl.h HAVE_CURL)