Introduce GoogleTest-based unit tests.

This patch introduce the first GoogleTest-based unit test for the emulator
sources. The goal here is to be able to easily automate the testing of the
Android-specific code in the emulator (i.e. really what's under android/),
since making the same for QEMU is essentially impossible.

+ Introduce 'emulator-libgtest' and 'emulator64-libgtest' host static
  libraries, built from the sources from extern/gtest. The reason the
  Android.mk module definitions in this directory are not used are
  mainly because we need to build both the 32-bit and 64-bit libraries
  at the same time, which the platform build doesn't support easily.

  Also, this will be reused later for the GPU emulation libraries
  when built with the standalone build.

+ Only a single test is added here, more as a proof-of-concept.
  To run the test suite, invoke the 'emulator_unittests' or
  'emulator64_unittests' program(s).

+ Note that unit-tests are written in C++, adding more tests might
  require fixing our headers to be included in this language.

BUG=NONE

Change-Id: If518ba30e38f202a4214ffd258fa5a07d6e48868
6 files changed