build: find FILE_OFFSET_BITS via array

build: find FILE_OFFSET_BITS via array

This makes cross-compiling happy, use a trick similar to autoconf's
AC_CHECK_SIZEOF macro.
Basically we make an array:

static int array[1 - 2 * !(((long int)(sizeof(off_t))) < 8)];

This gives -1 multiplied by the negation of the condition
(sizeof(off_t) < 8) cast to a long int.
So if the condition is true it gives array[(-1 * 0)] (remember the
condition is cast and negated) thus passing a build test with a 0-sized
array.
If it's false it gives array[(-1 * 1)] thus failing with a
negative-sized array.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Tue Feb 18 23:18:32 CET 2014 on sn-devel-104