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/libstore/builtins/fetchurl.cc b/third_party/nix/src/libstore/builtins/fetchurl.cc
index f3ef77fbd6..c3f38a943f 100644
--- a/third_party/nix/src/libstore/builtins/fetchurl.cc
+++ b/third_party/nix/src/libstore/builtins/fetchurl.cc
@@ -61,7 +61,9 @@ void builtinFetchurl(const BasicDerivation& drv, const std::string& netrcData) {
   /* Try the hashed mirrors first. */
   if (getAttr("outputHashMode") == "flat")
     for (auto hashedMirror : settings.hashedMirrors.get()) try {
-        if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
+        if (!hasSuffix(hashedMirror, "/")) {
+          hashedMirror += '/';
+        }
         auto ht = parseHashType(getAttr("outputHashAlgo"));
         auto h = Hash(getAttr("outputHash"), ht);
         fetch(hashedMirror + printHashType(h.type) + "/" +