Enable ARM unwind support on QNX/ARM as well.

The QNX/gcc behaves the same as Linux when it comes to ARM unwinding
tables. Use the same support as on ARM. It may not work flawlessly yet,
but at least it fixes one of the QNX compilation issues.

Change-Id: I1592a18d62fd8d8738c5254a75c73e3608b3d38b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>