[tlbuild] Build instructions for clisp

[Karl Berry]

    There are two conflicting sets of instructions for building clisp:

      http://www.tug.org/svn/texlive/trunk/Build/source/utils/xindy/README-clisp
      http://www.tug.org/svn/texlive/trunk/Build/source/utils/README

I wrote the version in utils/README specifically for TL builders years
ago, when we first incorporated xindy.  I'll take a look and report to
Joachim.

Thanks,
K