[tlbuild] Building svn57874.tar.gz (from github)

[Karl Berry]

    I'd assume that configure should stop immediately if an unsupported 
    option is used,

--with and --enable are exceptions to that; there, unrecognized options
are simply ignored. Per GNU standards, since the beginning.

This is a good thing in general because then one can create a general
list of --with / --enable and pass them to all packages that one is
building without having to worry about what matters to a given package.

Admittedly for TL it might be nicer to complain if an unrecognized
--with / --enable was given, but I confess it's not something I
especially want to spend time on.

I guess I could make the options be an error now. I thought I had made
them into no-ops, but sadly never tried them. --best, karl.