Avoid misinterpreting mgetgroups failure in running root-only tests.

[Jim Meyering]

Just heard about this on IRC:

        Avoid misinterpreting mgetgroups failure in running root-only tests.
        * src/setuidgid.c (main): Don't misinterpret as size_t an error
        return from mgetgroups.  Reported by Theodoros V. Kalamatianos.

diff --git a/src/setuidgid.c b/src/setuidgid.c
index 0f551f9..83369fd 100644
--- a/src/setuidgid.c
+++ b/src/setuidgid.c
@@ -1,5 +1,5 @@
 /* setuidgid - run a command with the UID and GID of a specified user
-   Copyright (C) 2003-2007 Free Software Foundation, Inc.
+   Copyright (C) 2003-2008 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -181,10 +181,11 @@ main (int argc, char **argv)
 #if HAVE_SETGROUPS
     if (n_gids == 0)
       {
-        n_gids = mgetgroups (pwd->pw_name, pwd->pw_gid, &gids);
-        if (n_gids <= 0)
+        int n = mgetgroups (pwd->pw_name, pwd->pw_gid, &gids);
+        if (n <= 0)
           error (1, errno, _("failed to get groups for user %s"),
                  quote (pwd->pw_name));
+        n_gids = n;
       }

     if (setgroups (n_gids, gids))