[tlbuild] Building without ICU

[Karl Berry]

    What's the magic command to exclude any binaries from TL build that
    depend on ICU?

I'm not sure there is one. Maybe --without-icu? I see some tests for
that in the source, although it doesn't show up in configure --help.
(I don't know why not, seems like a deficiency.)

A quick shows that at least these programs that depend on it:
  bibtexu upmendex xetex 

Hope it helps,
Karl