[tlbuild] hpux, xetex

[Karl Berry]

            for f in $(SOMEVAR) ; do

Thanks Arthur.

So it would seem the answer is to change the Makefiles like this:
test -z "$(SOMEVAR)" || for f in ...


On other fronts, for background:

It is intentional and desirable that the SHELL envvar is not respected
by make, precisely because of users who use [t]csh or whatever.

Our configure does not, to my recollection, attempt to find the "best"
shell on a system (whatever that might be).  It always uses /bin/sh.
(See make/common.mk.)  It is not that hard to write Makefile rules to
work with every system's /bin/sh, and that's what we have always done.
(For GNU packages too, almost always.)  Especially now that we don't
have to deal with Ultrix

If you want to read about shell portability, try
http://www.gnu.org/software/autoconf/manual/html_node/Portable-Shell.html.

karl