Reduce unnecessary rebuilds of .dex files with restat=1

The .dex.toc files are created by dexdump, which outputs all
information in a .dex file which may affect compilation of
other modules.

For prebuilt java libraries and static java libraries, we'll
output empty .toc files and don't set restat=1. .dex.toc files
are necessary even for static java libraries because they can
be referenced by LOCAL_JAVA_LIBRARIES (instead of
LOCAL_STATIC_JAVA_LIBRARIES).

We don't use this optimization for apps build. We cannot build
dexdump for apps build due to lack of libc++.

Performance:

$ m && touch \
  frameworks/base/core/java/com/google/android/util/Procedure.java \
  && time m
Before: 3m48s
After: 1m46s

Bug: 24597504
Change-Id: Id1665923b414dee705dc60af4c021390a19ea26f