[RFC] config: runtime: tests: ltp: enable support for code coverage

[a-wai]

When enabling code coverage support using in-kernel GCOV, we must first reset coverage "recording" right before starting the test, then ensure we pack and upload the resulting artifacts.

The latter is implemented by POSTing the artifact to the storage server, providing the artifact name and URL as a LAVA test result using the following format:

artifact-upload:<artifact name>:<artifact URL>

This allows the pipeline to add the uploaded artifact(s) to the corresponding node so the information can be easily re-used at a later stage.

Depends on kernelci/kernelci-pipeline#1141

[a-wai]

Notes:

• some of the needed information could be encoded in job configs (e.g. the upload path and name) rather than the template, but it needs some more thinking to make things more generic
• likewise, the pre/post-processing could be template fragments to be included based on certain conditions

This PR in its current state is mostly aimed at testing how everything works together on a "real" pipeline instance, and trigger a discussion about the parts that could/should be rewritten in a more generic way.

[laura-nao]

likewise, the pre/post-processing could be template fragments to be included based on certain conditions

Agreed - since gcov only works on kernels with the right configs and adds some overhead, it makes sense to include the pre/post processing steps conditionally.

Other than that, it looks good to me and seems ready for initial testing on staging

[a-wai]

since gcov only works on kernels with the right configs and adds some overhead

FWIW the overhead is almost null, especially thanks to the check on L43-45:

          - GCDA=/sys/kernel/debug/gcov
          # Bail out if $GCDA doesn't exist (as GCOV is likely not enabled)
          - test -d ${GCDA} || exit 0

The idea of having included "sub"-templates would be more related to avoiding code duplication and easily enabling gcov support in different test templates, although if (and that's a big if for now) I can find a way to make the include conditional that'll be even better.