Relax annotation visibility so runtime includes build.

Previous behavior in M and earlier would allow annotations marked
VISIBILITY_BUILD to be visible to the runtime when they should not
have been. When targeting older sdks, revert to this behavior.

Bug: 28826610

(cherry-picked from commit 7e50a7a5)

Change-Id: I43d2328be41ec9f4e679b3151f586c0b87b38c7c