[tlbuild] pdftex rebuild on 8-byte architectures

[Karl Berry]

Bottom line for everyone: the pdftex binary has to be updated on all
platforms, not just 64-bit. Sorry for that.

    mm> From now the results of rebuilds of a specific branch should in theory
    always end up on a different URL than for trunk:
        https://dl.contextgarden.net/build/texlive/branches/branch2021/

Nice.

    intact and just commit changes to all the 32-bit engines and 64-bit
    linux musl as well.

Yeah.

    np> > I changed the pdftex version to 1.40.23 for this. It also includes two
    >
    > Unfortunately that was not a good idea, 

And yet not changing the version identification in any way seemed like
an even worse idea. I sat there looking at the --version output of the
new binary (same as the old binary) and just couldn't bring myself to
commit it like that.

Version numbers are a huge maintenance problem in general, like so much
else that is "shared" across engines.

    now we need to update all the other engines, too:

s/engines/platforms and formats/ I suppose (hope).
Which should have happened automatically when the binaries are updated.
It did for me. I think.

At least the original unportable code was pdftex-specific (not copied
around into other engines), as I understood it.

I did forget that changing the version number will also break .fmt
compatibility. --thanks/sorry, karl.