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.

"core-tests" includes 1.8 language features.

core-tests-hostdex does not appear to be used in this
branch but it is used in downstream branches.

Bug: 27113322
Bug: 26953739
(cherry-picked from commit 6917cb5)

Change-Id: Id70a78aad45d15bdd23537df438fbfcd126f38d3

JavaLibrary.mk

@@ -290,6 +290,7 @@ ifeq ($(LIBCORE_SKIP_TESTS),)
     LOCAL_STATIC_JAVA_LIBRARIES := sqlite-jdbc-host mockwebserver-host nist-pkix-tests-host
     LOCAL_JAVACFLAGS := $(local_javac_flags)
     LOCAL_MODULE_TAGS := optional
+    LOCAL_JAVA_LANGUAGE_VERSION := 1.8
     LOCAL_MODULE := core-tests-hostdex
     LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/JavaLibrary.mk
     include $(BUILD_HOST_DALVIK_JAVA_LIBRARY)