OSV-2020-1421 Segv on unknown address in clang::FunctionProtoType::FunctionProtoType

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=21119 Crash type: Segv on unknown address Crash state: clang::FunctionProtoType::FunctionProtoType clang::ASTContext::getFunctionTypeInternal GetFullTypeForDeclarator...