Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/Support/Errno.h b/linux-x64/clang/include/llvm/Support/Errno.h
index 35dc1ea..8069c36 100644
--- a/linux-x64/clang/include/llvm/Support/Errno.h
+++ b/linux-x64/clang/include/llvm/Support/Errno.h
@@ -34,9 +34,10 @@
 inline auto RetryAfterSignal(const FailT &Fail, const Fun &F,
                              const Args &... As) -> decltype(F(As...)) {
   decltype(F(As...)) Res;
-  do
+  do {
+    errno = 0;
     Res = F(As...);
-  while (Res == Fail && errno == EINTR);
+  } while (Res == Fail && errno == EINTR);
   return Res;
 }