Write error messages about duplicate OIDs to stderr

src/backend/catalog/genbki.pl

@@ -137,8 +137,8 @@ my $found = 0;
 foreach my $oid (keys %oidcounts)
 {
 	next unless $oidcounts{$oid} > 1;
-	print "Duplicate oids detected:\n" if !$found;
-	print "$oid\n";
+	print STDERR "Duplicate OIDs detected:\n" if !$found;
+	print STDERR "$oid\n";
 	$found++;
 }
 die "found $found duplicate OID(s) in catalog data\n" if $found;