Fix 32bit ARM build on AArch64

On AArch64 the personality syscall doesn't tell us that we're running in
64bit mode. However, it does implicitly by telling us that it's aarch64.

So treat it the same way we already treat ppc and s390.

Signed-off-by: Alexander Graf <agraf@suse.de>
Merge pull request #120 from agraf/master

Fix 32bit ARM build on AArch64