AI 144501: am: CL 144500 Added support for some extra make arguments for some testsuite.

  For instance the libstdc++ testsuite requires BIONIC_TESTS=1 to
  actually build the tests.
  * development/testrunner/test_defs.py:
  Parse the new extra_make_args attribute.
  * development/testrunner/runtest.py:
  Added support for extra make arguments. Some testsuite requires this to actually be built.
  Changed the log statement to log what is actually being done.
  * development/testrunner/test_defs.xml:
  Added extra make argument to enable the libstdc++ tests.
  Original author: niko

Automated import of CL 144501