ls-files: die instead of fprintf/exit in -i error

ls-files: die instead of fprintf/exit in -i error

When ls-files was called with -i but no exclude pattern, it was
calling fprintf(stderr, "...", NULL) and then exiting.  On Solaris,
passing NULL into fprintf was causing a segfault.  On glibc systems,
it was simply producing incorrect output (eg: "(null)": ...).  The
NULL pointer was a result of argv[0] not being preserved by the option
parser.  Instead of requesting that the option parser preserve
argv[0], use die() with a constant string.

A trigger for this bug was: `git ls-files -i`

Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>