bug#57949: git head; unportable test(1) operator

[Gregory Heytings]

> > > Makefile.in started using "==" as test(1) comparison operator.
> > >
> > > This is not portable, only bash supports it. POSIX mandates "=".
> >
> > Thanks, fixed!
>
> Gregory, why are there ZERO-WIDTH SPACE characters in the top-level 
> Makefile.in?  What purpose do they server, and why cannot we do the same 
> with ASCII characters?

Their purpose is to make the text behave exactly like the "CC", "ELC", 
"GEN", "INFO", ... messages printed by make.  If it's problematic to have 
zero-width space characters there, they could be removed and/or replaced 
by something else.