Merge change 6412 into donut

* changes:
  Pass compiler flags for C++ too, and add a flag that enables warnings about missing virtual destructors
tree: c9aa8767de209ec62faa28e3c42ed0a04c055176
  1. core/
  2. libs/
  3. target/
  4. tools/
  5. buildspec.mk.default
  6. cleanspec.mk
  7. envsetup.sh