OSV-2020-1469 Segv on unknown address in clang::Sema::ActOnTag

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19182 Crash type: Segv on unknown address Crash state: clang::Sema::ActOnTag clang::Parser::ParseEnumSpecifier clang::Parser::ParseDeclarationSpecifiers...