CA-125230: Fix compilation for 64 bit

Support pack use fixed build architecture.
Change to detect architecture to fix building on 64 bit architecture and
stay compatible with 32 bit one.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Acked-by: Germano Percossi <germano.percossi@citrix.com>

GitHub: closes #68 on xapi-project/sm