Fix C++03 build

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@288555 91177308-0d34-0410-b5e6-96231b3b80d8

include/variant

diff --git a/include/variant b/include/variant
index 45efc78..94c1ece 100644
--- a/include/variant
+++ b/include/variant
@@ -216,7 +216,7 @@
 
 class _LIBCPP_EXCEPTION_ABI bad_variant_access : public exception {
 public:
-  _LIBCPP_FUNC_VIS virtual const char* what() const noexcept;
+  _LIBCPP_FUNC_VIS virtual const char* what() const _NOEXCEPT;
 };
 
 } // namespace std