[tlbuild] Support for musl

[Norbert Preining]

> x86_64-pc-linux-musl

So should we for now go with Karl's suggestion and use
  x86_64-linuxmusl
as arch name and adjust the perl scripts to work with it? In this case
the net installer could be used on these platforms.

Norbert

--
PREINING Norbert                               http://www.preining.info
Accelia Inc.     +    JAIST     +    TeX Live     +    Debian Developer
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