style(3p/nix): Add braces around single-line conditionals r/771

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

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

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

1 files changed, 3 insertions, 1 deletions

diff --git a/third_party/nix/src/libexpr/attr-set.hh b/third_party/nix/src/libexpr/attr-set.hh
index e5a888d7e9..74a41a7e5d 100644
--- a/third_party/nix/src/libexpr/attr-set.hh
+++ b/third_party/nix/src/libexpr/attr-set.hh
@@ -51,7 +51,9 @@ class Bindings {
   iterator find(const Symbol& name) {
     Attr key(name, 0);
     iterator i = std::lower_bound(begin(), end(), key);
-    if (i != end() && i->name == name) return i;
+    if (i != end() && i->name == name) {
+      return i;
+    }
     return end();
   }