Address a comment.

Author: kazutakahirata

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -1319,8 +1319,10 @@ class CfiFunctionIndex {
 
   std::vector<StringRef> symbols() const {
     std::vector<StringRef> Symbols;
-    for (auto &[GUID, Syms] : Index)
+    for (auto &[GUID, Syms] : Index) {
+      (void)GUID;
       llvm::append_range(Symbols, Syms);
+    }
     return Symbols;
   }