Enable code-coverage for the oeedger8r-cpp repository.

[anakrish]

The GNU code-coverage will work on the C++ edger8r. Code-coverage is a nice metric to have.
Having code-coverage in the higher 90s helps improve confidence in the OE SDK tools; especially oeedger8r.

[BRMcLaren]

@anakrish From my end, I think this is accomplished and the dependencies are in the backend and you need the actual code integration. Unassigning myself, if this is incorrect please re-assign.

[anakrish]

@mingweishih Can you help me with the integration? We are now generating the cobertura xml too.