Second attempt to add iterator_range::empty()

Doing this makes MSVC complain that `empty(someRange)` could refer to
either C++17's std::empty or LLVM's llvm::empty, which previously we
avoided via SFINAE because std::empty is defined in terms of an empty
member rather than begin and end. So, switch callers over to the new
method as it is added.

https://reviews.llvm.org/D68439

llvm-svn: 373935
diff --git a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
index c20d7d1..4a886ac 100644
--- a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
@@ -88,7 +88,7 @@
 }
 
 void CtorDtorRunner::add(iterator_range<CtorDtorIterator> CtorDtors) {
-  if (empty(CtorDtors))
+  if (CtorDtors.empty())
     return;
 
   MangleAndInterner Mangle(