install lcov in Docker image if coverage is specified (#46404)
Summary:
As a step to enable C++ code coverage in PyTorch, we want to install `lcov` in the Docker image so that lcov is available to use later on in the process. `lcov` is now installed in all non-rocm non-cuda ubuntu images.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46404
Reviewed By: seemethere
Differential Revision: D24343450
Pulled By: janeyx99
fbshipit-source-id: 3fdab0c0f78c004488e115505740620417f76646
