Make the language version selection smarter

Any artifacts that are targeting SDK versions < 24
and not explicitly setting the LOCAL_JAVA_LANGUAGE_VERSION
are now defaulted to 1.7.

Bug: 27495650
Bug: 26753820
Bug: 27377071
(cherry-picked from commit decb797276462feb4311b04e493da18f942b882f)

Change-Id: I0734b6e690bea32def3dc435c9ce0bd90b845e79
1 file changed