Description of problem:

Standalone apps HttpClient throws due to using system libcurl instead of scl libcurl.

How reproducible:

$ scl enable rh-dotnet20 -- bash
$ dotnet new console -o console
$ cd console
$ cat >Program.cs <<EOF
using System;
using System.Net.Http;

namespace console
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                HttpClientHandler clientHandler = new HttpClientHandler()
                {
                    ServerCertificateCustomValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; }
                };
                using (var client = new HttpClient(clientHandler))
                {
                    var response = client.GetAsync("https://www.redhat.com").Result;
                    System.Console.WriteLine(response.StatusCode);
                }
            }
            catch (Exception e)
            {
                System.Console.WriteLine("Exception:");
                System.Console.WriteLine($"\t{e.Message}");
            }
        }
    }
}
EOF
$ dotnet run
OK
$ dotnet publish -r linux-x64
$ ./bin/Debug/netcoreapp2.0/linux-x64/publish/console 
Exception:
	One or more errors occurred. (The handler does not support custom handling of certificates with this combination of libcurl (7.29.0) and its SSL backend ("NSS/3.28.3").)
$ ldd ./bin/Debug/netcoreapp2.0/linux-x64/publish/System.Net.Http.Native.so
	linux-vdso.so.1 =>  (0x00007ffc515f0000)
	libcurl.so.4 => /lib64/libcurl.so.4 (0x00007f50dca34000)
...

Actual results:

Standalone app uses system libcurl.

Expected results:

Standalone app uses scl libcurl.

Additional info:

- In our documentation, we recommend doing framework-dependent deployment (i.e. not standalone). Still, users can opt to use standalone.

- '/opt/rh/rh-dotnet20/root/usr/lib64' contains a 'libcurl.so'. self-contained is looking for 'libcurl.so.4'. Adding a symlink (e.g. ln -s libcurl-httpd24.so.4.4.0 libcurl.so.4) makes standalone pick up scl libcurl.