Building fails if using futures-preview block_on

[HackerWithoutACause]

I have to following code:

use futures::executor::block_on;
use isahc::prelude::*;

fn main() {
    println!("{}", block_on(request()).unwrap());
}

async fn request() -> Option<String> {
    let mut response = isahc::get_async("https://httpbin.org/get").await.ok()?;
    Some(response.text_async().await.ok()?)
}

When building on MacOS verson 10.13.6 I get the following error message when trying to compile:

error: linking with `cc` failed: exit code: 1

and then after a wall of text

= note: ld: warning: text-based stub file /System/Library/Frameworks//Security.framework/Security.tbd and library file /System/Library/Frameworks//Security.framework/Security are out of sync. Falling back to library file for linking.
          ld: warning: text-based stub file /System/Library/Frameworks//CoreFoundation.framework/CoreFoundation.tbd and library file /System/Library/Frameworks//CoreFoundation.framework/CoreFoundation are out of sync. Falling back to library file for linking.
          ld: warning: text-based stub file /System/Library/Frameworks//CoreFoundation.framework/CoreFoundation.tbd and library file /System/Library/Frameworks//CoreFoundation.framework/CoreFoundation are out of sync. Falling back to library file for linking.
          Undefined symbols for architecture x86_64:
            "___isOSVersionAtLeast", referenced from:
                _sectransp_connect_step1 in libcurl_sys-3a24cc39d88bdc1b.rlib(sectransp.o)
                _sectransp_connect_step2 in libcurl_sys-3a24cc39d88bdc1b.rlib(sectransp.o)
          ld: symbol(s) not found for architecture x86_64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

[sagebind]

This seems to be the same issue as #68. Disabling default features and not including that static-curl feature should fix this issue for now.

[HackerWithoutACause]

It works! Thank you.