Enable crosvm sandbox for aarch64

Crosvm sandbox requires policy files, which the commit is adding. Besides,
the Android.bp files to install the policy files are as of now generated by
the new script

Bug: 150975128
Test: Android.bp generation script locally tested, rebuild*.sh not yet tested
Change-Id: I1dbdec56680484078a3bf61554c6d4b5f475da84
26 files changed