Set apex_available property

The marked library(ies) were available to the APEXes via the hand-written
whitelist in build/soong/apex/apex.go. Trying to remove the whitelist
by adding apex_available property to the Android.bp of the libraries.

Bug: 150999716
Test: m
Change-Id: Ic909209db629590fbde861a3727696484c38532f