[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/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 260dfa5..512a3df 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5051,7 +5051,7 @@
     return;
 
   // Store tags sorted and without duplicates.
-  std::sort(Tags.begin(), Tags.end());
+  llvm::sort(Tags.begin(), Tags.end());
   Tags.erase(std::unique(Tags.begin(), Tags.end()), Tags.end());
 
   D->addAttr(::new (S.Context)