Compile link-time thunks in codegen.

Prepare for experimenting with Baker read barrier marking
introspection entrypoints for JIT.

Test: m test-art-host-gtest
Test: Compare compiled boot*.oat before and after (no diff).
Test: Pixel 2 XL boots.
Bug: 36141117
Change-Id: Idb413a31b158db4bf89a8707ea46dd167a06f110
31 files changed