Включая libcurl в проект C

Это моя самая первая программа на языке Си, и я использую этот пример кода libcurl с их веб-сайта:

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if(curl) {
        curl_easy_setopt(curl, CURLOPT_URL, "https://google.com/");

#ifdef SKIP_PEER_VERIFICATION
        /*
         * If you want to connect to a site who isn't using a certificate that is
         * signed by one of the certs in the CA bundle you have, you can skip the
         * verification of the server's certificate. This makes the connection
         * A LOT LESS SECURE.
         *
         * If you have a CA cert for the server stored someplace else than in the
         * default bundle, then the CURLOPT_CAPATH option might come handy for
         * you.
         */ 
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
#endif

#ifdef SKIP_HOSTNAME_VERFICATION
        /*
         * If the site you're connecting to uses a different host name that what
         * they have mentioned in their server certificate's commonName (or
         * subjectAltName) fields, libcurl will refuse to connect. You can skip
         * this check, but this will make the connection less secure.
         */ 
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
#endif

        res = curl_easy_perform(curl);

        /* always cleanup */ 
        curl_easy_cleanup(curl);
    }
    return 0;
}

Итак, в xcode я создал "группу" под названием curl и добавил Все файлы в каталог curl:

И теперь я получаю эти ошибки сборки:

Что я делаю не так? Любой совет поможет, спасибо!