lvm_private::File::GetStream() can fail if m_options == 0
It's not clear from the header a File created with a descriptor will be
not be usable by many parts of LLDB unless SetOptions is also called,
but it is.
This is because those parts of LLDB rely on GetStream() to use the
file, and that in turn relies on calling fdopen on the descriptor. When
calling fdopen, GetStream relies on m_options to determine the access
mode. If m_options has never been set, GetStream() will fail.
This patch adds options as a required argument to File::SetDescriptor
and the corresponding constructor.