try to fix clippy

Author: daniel-noland

default.nix

@@ -212,6 +212,7 @@
 
   rust-toolchain = with rust-version;
     (toolchainPkgs.rust-bin.${channel}.${version}.${profile}.override {
+      extensions = [ "rust-src" "rust-std-x86_64-unknown-linux-musl" "rust-std-x86_64-unknown-linux-gnu" ];
       targets = targets;
     });