Workaround for hostid on Darwin 8/MacPPC

[C. Speare]

Output of uname -a:
Darwin ppc7447.local 8.9.0 Darwin Kernel Version 8.9.0: Thu Feb 22 
20:54:07 PST 2007; root:xnu-792.17.14~1/RELEASE_PPC Power Macintosh 
powerpc PowerMac10,1 Darwin

output of hostid --version:
hostid (GNU coreutils) 6.9

Built using gcc 4.0.4 [custom compiled] plus the Apple-provided as/ld. 
(Same result with gcc-3.3, the Apple-provided version, and gcc-4.0.1, the 
Apple-provided version.)

Expected output: something random-ish, ideally some hash of the IP address 
or such. Of course, the result relies on gethostid().

Actual output: 00000000

Repeatable: always

Details: As it turns out, gethostid() is implemented in MacOSX, but is 
broken. On at least this version of MacOSX, the call returns 0 no matter 
what. This could happen on other platforms that have a broken (or 
incorrect) gethostid() function.

A possible (but weak)  workaround is to test for the case where id is 0. 
Roughly speaking:

-----

ppc7447% diff -c hostid.c.orig hostid.c
*** hostid.c.orig       Thu May  3 22:06:29 2007
--- hostid.c    Thu May  3 22:09:01 2007
***************
*** 90,95 ****
--- 90,101 ----
       is a no-op unless unsigned int is wider than 32 bits.  */
    id &= 0xffffffff;

+   if (id == 0) {
+   /* id of 0 can't be right, so come up with some 32-bit random
+      value. */
+      id = random();
+   }
+
    printf ("%08x\n", id);

    exit (EXIT_SUCCESS);

-----

Or something along those lines. This isn't a bug in hostid as much as it 
is a brain-dead implementation of gethostid(), but catching a broken 
gethostid() certainly helps hostid to be more robust.

Thank you.