[tlbuild] pdftex rebuild on 8-byte architectures

[Karl Berry]

    pdfTeX 3.141592653-2.6-1.40.23 (TeX Live 2022/dev)
    kpathsea version 6.3.4/dev
      as opposed to
    pdfTeX 3.141592653-2.6-1.40.23 (TeX Live 2021)
    kpathsea version 6.3.3

Good point.

    (I don't know whether that really matters.)

It doesn't affect the behavior, but I suppose users may report confusion
with the "/dev" versions. Still, it's not exactly incorrect, so fine.
So I continue to think that whichever way is easier as the rebuild
source is ok.

Thanks to everyone who has rebuilt and/or committed already. -k