[tlbuild] Apply to be loongarch64-linux volunteer builder

[Karl Berry]

        I want to become a volunteer builder for loongarch64-linux.

Thanks much for offering.

   I have successfully build it by "./Build --debug --disable-luajittex
   --disable-luajithbtex --enable-build-in-source-tree
   --disable-mfluajit" (Because luajit not be merged to upstream yet but
   it's coming).

Thanks for sending the command. I'm surprised
--enable-build-in-source-tree actually worked, but cool :).

   What should I do to add it to the official network download channel.

I added a new section to the tlbuild web page with the variety of things
that can be provided:
https://tug.org/texlive/build.html#newsys

Please let me know if questions or problems, else I'll look forward to
the urls for download :). --thanks again, karl.