Remove support of disabling Jack.

We removed code and variables related to running dx on classes.jar in
this change. Also removed target emma rules (but kept the emma rules for
host java libraries), for it's now done by Jack.
We still support to build classes.jar (and javalib.jar for static Java
libraries) using javac, because tools like javadoc need class files as
Removed the obsolete install-dex-debug.

Bug: 27400061
Change-Id: If0bcdfe62cb181a98754fb0dbe1c12c92e38d3e8
12 files changed