Make CtsShim*Prebuilt be available to the test APEXes

android_app_import now supports apex_available property. Fill the
property for the CtsShim*Prebuilt apks so that they can be correctly
included in the test APEXes.

Bug: 154488897
Test: m
Change-Id: I9cf2e30bb38abbb33bf76a0eab0dc2a10a5647c9
1 file changed