ikiwiki-mass-rebuild: under $! before setting $) to avoid strange errno issue

This fixes a problem sgran saw on alioth. Apparently nss-db sets errno to
ENOENT as a side effect trying to read an optional file, but succeeds
anyway. Then, somehow, errno remains set across the library calls made by
$).

So unset it first as a workaround; there's probably a nss-db, libc, and/or
perl bug underneath.

debian/changelog

@@ -1,6 +1,7 @@
 ikiwiki (2.49) UNRELEASED; urgency=low
 
   * haiku: Generate valid xhtml.
+  * ikiwiki-mass-rebuild: under $! before setting $) to avoid strange errno issue
 
  -- Joey Hess <joeyh@debian.org>  Fri, 30 May 2008 19:08:54 -0400
 

ikiwiki-mass-rebuild

@@ -34,6 +34,7 @@ sub processline {
 	if (! $pid) {
 		my ($uuid, $ugid) = (getpwnam($user))[2, 3];
 		my $grouplist=join(" ", $ugid, $ugid, supplemental_groups($user));
+		undef $!;
 		$)=$grouplist;
 		if ($!) {
 			die "failed to set egid $grouplist: $!";