refactor(3p/nix): Apply clang-tidy's performance-* fixes r/789

This applies the performance fixes listed here:

https://clang.llvm.org/extra/clang-tidy/checks/list.html

1 files changed, 1 insertions, 1 deletions

diff --git a/third_party/nix/src/nix-build/nix-build.cc b/third_party/nix/src/nix-build/nix-build.cc
index 5090cbe51370..921fc2ba22d1 100644
--- a/third_party/nix/src/nix-build/nix-build.cc
+++ b/third_party/nix/src/nix-build/nix-build.cc
@@ -299,7 +299,7 @@ static void _main(int argc, char** argv) {
   if (readStdin) {
     exprs = {state->parseStdin()};
   } else {
-    for (auto i : left) {
+    for (const auto& i : left) {
       if (fromArgs) {
         exprs.push_back(state->parseExprFromString(i, absPath(".")));
       } else {