CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CAPATH, char *capath);
DESCRIPTIONPass a char * to a zero terminated string naming a directory holding multiple CA certificates to verify the peer with. If libcurl is built against OpenSSL, the certificate directory must be prepared using the openssl c_rehash utility. This makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER(3) option.
The CURLOPT_CAPATH(3) function apparently does not work in Windows due to some limitation in openssl.