Upstream: No, not upstreamable like this
Reason: We want the rustup binary in $CARGO_HOME/bin to be of the
same version as the one we distribute in this rustup package.
--- src/rustup-cli/self_update.rs.1	2018-12-13 21:56:55.211778812 +0100
+++ src/rustup-cli/self_update.rs	2018-12-13 21:56:42.763779768 +0100
@@ -671,8 +671,7 @@
     if rustup_path.exists() {
         utils::remove_file("rustup-bin", rustup_path)?;
     }
-    utils::copy_file(this_exe_path, rustup_path)?;
-    utils::make_executable(rustup_path)?;
+    utils::symlink_file(this_exe_path, rustup_path)?;
     install_proxies()
 }