Downloading the binaries through a proxy if either HTTPS_PROXY or HTT…

…P_PROXY environment variable is set.

closes #29

build.rs

@@ -45,7 +45,17 @@ fn main() {
         let url = format!("{}/{}", GITHUB_URL, download_filename);
         let mut downloaded_bytes = Vec::new();
 
-        let _size = ureq::get(&url)
+        let http_proxy = std::env::var("HTTPS_PROXY").or_else(|_| std::env::var("HTTP_PROXY"));
+        let agent = if let Ok(proxy) = http_proxy {
+            let proxy = ureq::Proxy::new(proxy).unwrap();
+            ureq::AgentBuilder::new()
+                .proxy(proxy)
+                .build()
+        } else {
+            ureq::AgentBuilder::new().build()
+        };
+
+        let _size = agent.get(&url)
             .call()
             .unwrap()
             .into_reader()