clearing env for make check

[Roland McGrath]

> Roland McGrath <roland@frob.com> writes:
> 
> > Then, I'd change all the tests et al to pass --ignore-environment
> > along with --library-path.
> > 
> > If this sounds good, then I can implement it.
> 
> Do we need another option?  Can't we simply test for the variables in
> the toplevel Makefile and fail right away if any is defined?

Well, maybe you want it for running your compilers or whatnot.  It's only
when running our own programs via ld.so that we have any business telling
somebody what preloads they might want in their life.  But I wouldn't
object to what you suggest.