[CI] Soft fail merge coverage reports step

[ycombinator]

What does this PR do?

This PR makes it so that if the "Merge coverage reports" step (key: merge-coverage) in CI fails, we don't fail the build. Since the SonarQube step depends on the merge-coverage step, we similarly don't fail the build if that step fails too, which is expected to happen if the merge-coverage step doesn't succeed.

Why is it important?

We've observed that in some Agent PRs (example), if the "Merge coverage reports" step is retried, it fails like so:

$  .buildkite/scripts/steps/merge.sh unit-tests-2204 unit-tests-2204-arm64 unit-tests-win2016 unit-tests-win2022 unit-tests-macos-13 unit-tests-win10 unit-tests-win11
--
  | go: downloading github.com/wadey/gocovmerge v0.0.0-20160331181800-b5bfa59ec0ad
  | go: finding module for package golang.org/x/tools/cover
  | go: downloading golang.org/x/tools v0.25.0
  | go: found golang.org/x/tools/cover in golang.org/x/tools v0.25.0
  | 2024-09-20 15:54:06 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-2204"
  | 2024-09-20 15:54:06 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-2204
  | 2024-09-20 15:54:06 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:06 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-2204-arm64"
  | 2024-09-20 15:54:07 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-2204-arm64
  | 2024-09-20 15:54:07 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:07 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-win2016"
  | 2024-09-20 15:54:07 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-win2016
  | 2024-09-20 15:54:08 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:08 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-win2022"
  | 2024-09-20 15:54:08 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-win2022
  | 2024-09-20 15:54:09 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:09 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-macos-13"
  | 2024-09-20 15:54:09 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-macos-13
  | 2024-09-20 15:54:09 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:09 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-win10"
  | 2024-09-20 15:54:09 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-win10
  | 2024-09-20 15:54:10 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024-09-20 15:54:10 INFO   Searching for artifacts: "coverage.out" within step: "unit-tests-win11"
  | 2024-09-20 15:54:10 INFO   Found 1 artifacts. Starting to download to: /buildkite/builds/bk-agent-prod-k8s-1726847620841271029/elastic/elastic-agent/unit-tests-win11
  | 2024-09-20 15:54:11 INFO   Successfully downloaded "coverage.out" 7.6 MiB
  | 2024/09/20 15:54:11 OVERLAP BEFORE: github.com/elastic/elastic-agent/internal/pkg/agent/cmd/run.go {132 40 134 3 1 0} {133 2 133 40 1 0}
  | 🚨 Error: The command exited with status 1
  | user command error: exit status 1

For now, we're temporarily going to skip this step while we investigate the root cause and failure separately.

[mergify]

This pull request does not have a backport label. Could you fix it @ycombinator? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-v8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[blakerouse]

+1

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube