vipw: flush stdout before getting answer.

Otherwise the question is displayed only after the user presses Return,
and the program looks like it's hanging.

This happens at least on musl libc.

Reported by @loreb.

Signed-off-by: Érico Nogueira <erico.erc@gmail.com>

login-utils/vipw.c

@@ -353,6 +353,7 @@ int main(int argc, char *argv[])
 		 * which means they can be translated. */
 		printf(_("Would you like to edit %s now [y/n]? "), orig_file);
 
+		fflush(stdout);
 		if (fgets(response, sizeof(response), stdin) &&
 		    rpmatch(response) == RPMATCH_YES)
 			edit_file(1);