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/optimise-store.cc b/third_party/nix/src/libstore/optimise-store.cc
index 450f31c59f10..ad37190236e9 100644
--- a/third_party/nix/src/libstore/optimise-store.cc
+++ b/third_party/nix/src/libstore/optimise-store.cc
@@ -115,7 +115,9 @@ void LocalStore::optimisePath_(OptimiseStats& stats, const Path& path,
 
   if (S_ISDIR(st.st_mode)) {
     Strings names = readDirectoryIgnoringInodes(path, inodeHash);
-    for (auto& i : names) optimisePath_(stats, path + "/" + i, inodeHash);
+    for (auto& i : names) {
+      optimisePath_(stats, path + "/" + i, inodeHash);
+    }
     return;
   }