Must choose one of nptl, linuxthreads

[Roland McGrath]

> It seems that --enable-add-ons can no longer be used without arguments,
> or what is the matter?

That is true, you will try to get both nptl and linuxthreads.
This has always been the case for as long as both directories have been there.

It is the case that you must enable tls to build nptl, but that is not what
you mentioned.  As far as I can recall, there has never been any magic
add-on selection associated with using --with-tls.  That would not be
desireable.