Make ApexManagerTest use resources that are not prebuilt

Currently ApexManagerTest uses a prebuilt apex for testing. This
resource was built in a dev environment and targets R, which is not a
valid version on release builds.

This CL replaces the prebuilt resource with one that gets rebuilt
whenever the test is run.

Bug: 155242557
Test: atest ApexManagerTest
Change-Id: Id6e9e9f688b07da1ad80f44f7486d7266e3a21f3