Merge libdexfile_external into libdexfile (reland 2).

To reduce the number of DSO's. libdexfile_external only adds a few
small functions on top of libdexfile, and it's still only those
functions that are available in the APEX stubs.

Also rename libdexfile_external_static to libdexfile_static, for
consistency.

Since libdexfile now has stubs, we need to add test_for properties to
avoid linking against the stubs in tests.

This relands https://r.android.com/1666119 that got submitted out of
order from https://r.android.com/1664026 - prerequisite changes now
submitted with https://r.android.com/1671709.

Test: Flash and boot with userdebug and eng to try both release and
  debug modules.
Test: art/tools/buildbot-build.sh {--target,--host}
Test: art/build/apex/runtests.sh
Test: mmm art
Bug: 143978909
Change-Id: I6de99052d6d8a9d01d748baabbbcecfe1f4509dc
13 files changed