The following patch makes coreutils/test.c act fail gracefully if getgroups()
returns a -1. This fixes a problem on the One Laptop Per Child ROM image
whereby we were getting odd Memory exhausted messages for '[' and 'test'.
Found by Mitch Bradley <wmb@firmworks.com>
(Tweaked by Rob: no need to initialize a static to NULL, or realloc something
that's only allocated when it's NULL.)