cannot compile curl on MacOS Mojave

[Guy-kun]

Cloning the latest version and attempting to run
./build.sh -p=mac --libs=curl --arch=x86_64 --mode=release

Results in the error:

connect.c:1087:12: error: 'connectx' is only available on macOS 10.11 or newer
[-Werror,-Wunguarded-availability]

Which seems to be related to a libcurl issue that has since been patched:
curl/curl#2080

I'm not well versed enough in how this build process works but if someone could possibly take a look as to what needs to be changed to use latest libcurl this will likely fix the issue.

Thanks!