modern sync: suppport proxy in edenapi http client

Summary: We need this to be able to reach AWS's edenapi.

Reviewed By: andreacampi

Differential Revision: D66759176

fbshipit-source-id: af9c4ecd376045580b692d4f33907edf6ab7cd0f

eden/scm/lib/http-client/src/request.rs

@@ -673,6 +673,11 @@ impl Request {
         easy.verbose(self.verbose)?;
         easy.unix_socket_path(self.auth_proxy_socket_path)?;
 
+        match std::env::var("HTTP_PROXY") {
+            Ok(proxy) => easy.proxy(&proxy)?,
+            Err(_) => (),
+        }
+
         // Configure the handle for the desired HTTP method.
         match easy.get_ref().request_context().method() {
             Method::Get => {}