Support for setting CURLSSLOPT_NATIVE_CA on Windows

[pr0g]

This might be an issue but it's also very likely this is possible and I just don't know how to do it.

I am using aws-sdk-cpp on Windows and have a custom build of OpenSSL and Curl. When I try to make an https request using Curl directly, I get the error:

 SSL peer certificate or SSH remote key was not OK

I can fix this by either setting a certificate with

curl_easy_setopt(curl, CURLOPT_CAINFO, "cacert.pem");

(Where "cacert.pem" is one I grabbed from here).

Or I can use:

curl_easy_setopt(curl, CURLOPT_SSL_OPTIONS, CURLSSLOPT_NATIVE_CA);

Where CURLSSLOPT_NATIVE_CA states "Tell libcurl to use the operating system's native CA store for certificate verification" (see here for more info).

The problem with this option is I don't see a way to pass that through to AWS SDK. I can get things to work if I use:

Aws::Client::ClientConfiguration client_config;
client_config.region = "<my-region>";
client_config.caFile = "cacert.pem";

But it would be nice if I could just use the operating system's native CA store.

Is there a way to do this that I'm not seeing? I initialize Curl outside of aws-sdk-cpp and I've tried setting the property right after curl_global_init(CURL_GLOBAL_ALL);.

Something like...

curl_global_init(CURL_GLOBAL_ALL);

if (CURL* curl = curl_easy_init()) {
  curl_easy_setopt(curl, CURLOPT_SSL_OPTIONS, CURLSSLOPT_NATIVE_CA);
}

Aws::SDKOptions options;
options.httpOptions.initAndCleanupCurl = false;
Aws::InitAPI(options);

...

Aws::ShutdownAPI(options);
curl_global_cleanup();

But that unfortunately does not seem to work. If there's a way to do this I'd be really curious to know. Thank you!

[pr0g]

Moved to #2733