[tex4ht] debugging tex4ht bootstrap

[Karl Berry]

    I'll see if I can sort it out.

That would be fantastic, Deimi.  Having a reproducible environment would
be so great.  (E.g., be able to do a checkout and type "make" and it
just works ...)  I've got it in my queue, but ...

    The first compilation fails, but not others.

For debugging, I found that making xhlatex (and htlatex) be
#!/bin/sh -e was helpful, since then it stopped after the first (failed) run.

Something similar was going wrong for me with tex4ht-options.tex (which
generates tex4ht.4ht).

There also seems to be a mutual dependency problem wrt tex4ht-4ht.tex
and tex4ht-cond4ht.tex.  The former creates mktex4ht.cnf and then
\input's cond4ht.4ht.  But to make cond4ht.4ht, mktex4ht.cnf needs to
already exist.  It seems.  Maybe I'm wrong.  I'm unsure of everything.

In general, the relationship of the pieces remains an inscrutable
mystery to me :(.  --karl