tlpretest: two problems: optex bad linked, old linux libc.so not supported

[Karl Berry]

    should be linked: -> luahbtex, (no luatex, it will cause errors).

Sorry. I changed it in one place but failed to remember to do it
everywhere.
    
    The more libc.so versions are supported by the binary, the fewer TeXlive 
    users will be in trouble.

I am well aware.  The problem is that CentOS 7 is no longer supported
(by RH/CentOS/Alma/Rocky/etc.), even for security fixes.  Thus it is
imprudent to compile on it.  (Or for anyone to use it.)

Thus we had to switch to the oldest supported version, namely RHEL 8
(Rocky 8, Alma 8, etc.).

I wish it were possible to compile on newer distro versions in a way
that's compatible with older versions, but as far as I know, it isn't.

Besides the CG farm, Nelson does compile on older systems, including
CentOS 7.  http://ftp.math.utah.edu/pub/texlive-utah-2025/

I know it's inconvenient not to be supported out of the box.  Sorry.
But I don't see a rational alternative.  -k