Fix build on x32

Recognize x32 and disable JIT in this configuration.

Task-number: QTBUG-35463
Change-Id: Ie5bf64f22f3e58a9b3f12190cf790ad6c39f415e
Reviewed-by: Gregory Hinton Nietsky <gregory@distrotech.co.za>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>