[RenderScript] Remove LOCAL_JACK_ENABLED := disabled

Bug: 27338966

  - Now fw/rs/update_rs_prebuilts.sh explicitly ask JACK to produce the
    jar file for support lib, LOCAL_JACK_ENABLED := disabled is not
    necessary anymore.

Change-Id: I3aa199e86d253106bce7f47ecfc25b17e991e958
(cherry picked from commit ea5ddd5d6441f0be21fc5d3c4107028046e533a0)
diff --git a/v8/renderscript/Android.mk b/v8/renderscript/Android.mk
index ea42d74..17e06c0 100644
--- a/v8/renderscript/Android.mk
+++ b/v8/renderscript/Android.mk
@@ -28,11 +28,6 @@
 LOCAL_SRC_FILES := $(call all-java-files-under, java/src)
 LOCAL_JAVA_LIBRARIES := android-support-annotations
 
-# Disable JACK when RSTest_Compatlib is used for updating RS prebuilts.
-ifneq (,$(UPDATE_RS_PREBUILTS_DISABLE_JACK))
-LOCAL_JACK_ENABLED := disabled
-endif
-
 LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)