Update Clang for LLVM split stack API changes in r205997

Patch by Alex Crichton!

llvm-svn: 205998
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index ca8b99a..e82b6de 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1090,6 +1090,8 @@
     FuncAttrs.addAttribute(llvm::Attribute::NoRedZone);
   if (CodeGenOpts.NoImplicitFloat)
     FuncAttrs.addAttribute(llvm::Attribute::NoImplicitFloat);
+  if (CodeGenOpts.EnableSegmentedStacks)
+    FuncAttrs.addAttribute("split-stack");
 
   if (AttrOnCallSite) {
     // Attributes that should go on the call site only.