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/nix/command.cc b/third_party/nix/src/nix/command.cc
index 1825bb6136be..4c1220668c8a 100644
--- a/third_party/nix/src/nix/command.cc
+++ b/third_party/nix/src/nix/command.cc
@@ -111,7 +111,9 @@ void StorePathsCommand::run(ref<Store> store) {
   if (all) {
     if (installables.size())
       throw UsageError("'--all' does not expect arguments");
-    for (auto& p : store->queryAllValidPaths()) storePaths.push_back(p);
+    for (auto& p : store->queryAllValidPaths()) {
+      storePaths.push_back(p);
+    }
   }
 
   else {