A similar option already exists in
packages/modules/Connectivity/Cronet/apex/Android.bp. This is in
preparation of adding cronet to framework-tethering. It is possible that
we only end up using one of the variables but better safe than sorry.

This change will be blocked by the blocked automerger into
tm-mainline-prod. If this continues to be a problem, we might have to
play some tricks with automerger.

Test: TH
Change-Id: I40ba22aba041ec12ec2bf2881df14e6c0ee53b44