[tlbuild] tl branch rebuild again

[Karl Berry]

Just in case you don't have an svn checkout of the branch already, you
can get it with (for instance):

  svn co svn://tug.org/texlive/branches/branch2018/Build/source


Or you can get it by rsync this way if you prefer that:

  mkdir tl18branch
  cd tl18branch
  rsync -a --delete --exclude=.svn tug.org::tlbranch .

The only thing in that branch directory via rsync is the compilable
sources.

Thanks,
Karl