Handle apps that share a UID with the system_server correctly.

The system process does not explicitly declare any ABI, or
package any native code that it depends on but its ABI is
dictated by the zygote configuration. We need to account for
it correctly to have apps that share a UID with it work
correctly.

bug: 16317188

Change-Id: I84713c64409d7fdcc314114231e87a9263d5c5e7