Add test asserting setup on devices using flattened apexes

This test will only be run on aosp_cf_x86_phone_noapex target and has
two main goals:
1. Assert that aosp_cf_x86_phone_noapex actually uses flattened apexes.
2. Assert that flattened apexes setup is what we expect.

Bug: 135516420
Test: atest flattened_apex_test on aosp_cf_x86_phone_noapex succeeds
Test: atest flattened_apex_test on aosp_blueline fails
Test: atest --test-mapping system/apex/apexd doesn't include flattened_apex_test
Change-Id: I364d8563d94a2345ebf89cb4d6502481f85b2cd3
3 files changed
tree: e6aa7912065a37e0fa7fa5638475097228e14228
  1. apexd/
  2. apexer/
  3. docs/
  4. proto/
  5. shim/
  6. tests/
  7. CleanSpec.mk
  8. OWNERS
  9. PREUPLOAD.cfg