When linking against .jack files that contain 1.8 language
features Jack (currently) requires -D jack.java.source.version=1.8.
"core-tests" includes 1.8 language features.
Bug: 27113322
Bug: 26953739
(cherry-picked from commit a835180b74af2cad853db08e8d41a7b04773759b)
Change-Id: I2be4db6788b14558f74534c24bb007f7fb8b6b67