[ci/build] Add label for building example plugins

[jbudz]

Adds support for including example plugins in a distribution, and the subsequent Cloud deployment. Previously we did support building all of the example plugins, but they weren't installed.

Opening this up for review with a major caveat: functional tests are broken when example plugins are enabled. Mostly due to snapshots finding a bunch of new plugins. I was planning on closing this out, but:

• PR authors will have a way to manually test code that doesn't get shipped
• We can replace the demo environment (and management) with cloud deployments

[jbudz]

fyi @walterra. This works but probably not something I can merge - it breaks a whole bunch of tests.

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[spalger]

functional tests are broken when example plugins are enabled. Mostly due to snapshots finding a bunch of new plugins.

Are the example plugins installed into ${dist}/plugins? Maybe we can remove the plugins in https://github.com/elastic/kibana/blob/f7f8fa6553c296cf57b0c86a4c80ab3b603a668c/.buildkite/scripts/download_build_artifacts.sh#L16? I'm thinking something to the effect of:

if is_pr_with_label "ci:build-example-plugins"; then
  rm -rf "$KIBANA_BUILD_LOCATION/plugins";
  mkdir "$KIBANA_BUILD_LOCATION/plugins";
fi

In fact the if condition might not even be necessary, maybe we just ensure the distributable we install for testing has no plugins

[kibana-ci]

:green_heart: Build Succeeded

• Buildkite Build
• Commit: b8b301c7b456cb46cf5eef037ae2143bcfbdcef9
• Cloud Deployment

Metrics [docs]

✅ unchanged

History

• :green_heart: Build #75739 succeeded b81d486a24b0443f1f894a658c126737be8f5ad7
• :broken_heart: Build #75690 failed 200dea7c27cf0770e6b84ce1c2ba9f53298ea589
• :yellow_heart: Build #74179 was flaky fc92113b03657569bd604cb3fd1e98a7d4f3dd64
• :green_heart: Build #69842 succeeded a769d180130a42fc2058879bff7bd808fbd9f0e8
• :green_heart: Build #68533 succeeded 5bd42e88c50c2e2728699eab6575b0bfe9b54210

To update your PR or re-run it, just comment with: @elasticmachine merge upstream

[spalger]

@jbudz did that idea end up working?

[jbudz]

:+1: it did, thank you for the pointer.