use __BIONIC__ not __ANDROID__

This is more correct since this is a feature of the C library in use,
and not actually Android specific.

This matches version of patch that went upstream:
  http://git.netfilter.org/iptables/commit/?id=9dd0c484767c9fa3852b23c790d3d5e84e510beb

Test: builds
Bug: 143044679
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Iec8088a51b471a8b10a28c0ac8c4badf60bbbe5f
Merged-In: Iec8088a51b471a8b10a28c0ac8c4badf60bbbe5f