Issue title: [Request] Update curl to support TLS v1.3
 Issue body: Currently, ios_system's curl can't download a HTTPS site's content using TLS v1.3.

I think that you built curl 7.51.0 with `--with-darwinssl` flag. If so, is it possible to update curl to 7.56.1 or later?

curl with darwinssl has supported TLS v1.3 since [7.56.1](https://curl.se/changes.html#7_56_1).
 Comments: 
 Comment 0: actually curl with darwinssl isn't supporting TLS 1.3 because SecureTransport isn't supporting TLS 1.3, see https://github.com/curl/curl/issues/4524 .

so we need to build cURL with other ssl libraries, like openssl, LibreSSL, NSS, etc...
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