style(3p/nix): Add braces around single-line for-loops r/772

These were not caught by the previous clang-tidy invocation, but were
instead sorted out using amber[0] as such:

    ambr --regex 'for (\(.+\))\s([a-z].*;)' 'for $1 { $2 }'

[0]: https://github.com/dalance/amber

1 files changed, 3 insertions, 1 deletions

diff --git a/third_party/nix/src/libstore/local-fs-store.cc b/third_party/nix/src/libstore/local-fs-store.cc
index c1efbb76d8..d9eaea2e93 100644
--- a/third_party/nix/src/libstore/local-fs-store.cc
+++ b/third_party/nix/src/libstore/local-fs-store.cc
@@ -48,7 +48,9 @@ struct LocalStoreAccessor : public FSAccessor {
     auto entries = nix::readDirectory(realPath);
 
     StringSet res;
-    for (auto& entry : entries) res.insert(entry.name);
+    for (auto& entry : entries) {
+      res.insert(entry.name);
+    }
 
     return res;
   }