Allow dex2oat to create a full class loader context

We previously checked that dex2oat sees only a single class loader. This
CL removes the restriction and enables dex2oat to create and compile with
a full class loader context.

Test: m test-art-host
Bug: 38138251
Change-Id: I03e75a75757995ce8ce3addf0bc0a708e18ac050
7 files changed