[clang] Change std::sort to llvm::sort in response to r327219

r327219 added wrappers to std::sort which randomly shuffle the container before
sorting.  This will help in uncovering non-determinism caused due to undefined
sorting order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of
std::sort.

llvm-svn: 328636
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index ae29e7e..dea1c2e 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -10688,8 +10688,8 @@
     // in general, want to list every possible builtin candidate.
   }
 
-  std::sort(Cands.begin(), Cands.end(),
-            CompareTemplateSpecCandidatesForDisplay(S));
+  llvm::sort(Cands.begin(), Cands.end(),
+             CompareTemplateSpecCandidatesForDisplay(S));
 
   // FIXME: Perhaps rename OverloadsShown and getShowOverloads()
   // for generalization purposes (?).