Re: "configure" tries to execute what seems to be a shell command.

[Paul Eggert]

Thanks for reporting that. I just now rebuilt sed-4.8's 'configure' script with 
Autoconf master (which advertises itself as version 2.69.301-14265) and the 
problem seems to have been fixed there. We're planning Autoconf 2.70 for soon, 
and the bug should be fixed once that comes out.