Add flags needed to switch Jack to 1.8 for CTS targets

When linking against .jack files that contain 1.8 language
features Jack (currently) requires -D jack.java.source.version=1.8.
This requirement may be dropped in future and then this change
might be reverted. It may also be removed once 1.8 becomes
the default. See bug 27113322.

"core-tests" includes 1.8 language features.

Bug: 26814204
Bug: 27113322
Bug: 26953739
Change-Id: I7e23e98bb474f78236bc5e8f210fbae8f89e2b86
1 file changed