Introduce error_exit as a noreturn variant of error (EXIT_FAILURE, ...)

Introduce error_exit as a noreturn variant of error (EXIT_FAILURE, ...)

error (EXIT_FAILURE, ...) should be noreturn but on some systems it
isn't.  This may cause warnings about code that should not be
reachable.  So have an explicit error_exit wrapper that is noreturn
(because it calls exit explicitly).  Use error_exit in all tools under
the src directory.

https://bugzilla.redhat.com/show_bug.cgi?id=2068692

Signed-off-by: Mark Wielaard <mark@klomp.org>