Clang diagnoses the inconsistent noexcept-specifier on the friend
declaration of __get. Add it, and also on __get_storage.
PR libstdc++/90397
* include/std/variant (_Variant_storage<false, Types...>::_M_storage())
(_Variant_storage<true, Types...>::_M_reset()))
(_Variant_storage<true, Types...>::_M_storage())): Add noexcept.
(__get_storage): Likewise.
(variant): Add noexcept to friend declarations for __get and
__get_storage.
From-SVN: r271079
4b7a3ab82f