[7.17](backport #38162) PoC: use pipeline generator (#38485)

This commit introduces a main pipeline generator similar to the one used with Jenkins #20104 to help with the migration to Buildkite.

Co-authored-by: Pavel Zorin <pavel.zorin@elastic.co>
Co-authored-by: Alexandros Sapranidis <alexandros@elastic.co>
(cherry picked from commit 4b7467b)

Co-authored-by: Victor Martinez <victormartinezrubio@gmail.com>

.buildkite/auditbeat/scripts/unit-tests.sh

@@ -5,6 +5,5 @@ set -euo pipefail
 echo "--- Running Unit Tests"
 sudo chmod -R go-w auditbeat/
 
-cd auditbeat
 umask 0022
-mage build unitTest
+mage -d auditbeat build unitTest

.buildkite/buildkite.yml

@@ -0,0 +1,44 @@
+projects:
+    - "auditbeat"
+    - "deploy/kubernetes"
+    - "filebeat"
+    - "heartbeat"
+    - "libbeat"
+    - "metricbeat"
+    - "packetbeat"
+    - "winlogbeat"
+    - "x-pack/auditbeat"
+    - "x-pack/dockerlogbeat"
+    - "x-pack/filebeat"
+    - "x-pack/functionbeat"
+    - "x-pack/heartbeat"
+    - "x-pack/libbeat"
+    - "x-pack/metricbeat"
+    - "x-pack/osquerybeat"
+    - "x-pack/packetbeat"
+    - "x-pack/winlogbeat"
+
+## Changeset macros that are defined here and used in each specific 3.0 pipeline.
+changeset:
+    ci:
+        - "^Jenkinsfile"
+        - "^\\.ci/scripts/.*"
+    oss:
+        - "^go.mod"
+        - "^pytest.ini"
+        - "^dev-tools/.*"
+        - "^libbeat/.*"
+        - "^testing/.*"
+    xpack:
+        - "^go.mod"
+        - "^pytest.ini"
+        - "^dev-tools/.*"
+        - "^libbeat/.*"
+        - "^testing/.*"
+        - "^x-pack/libbeat/.*"
+
+disabled:
+    when:
+        labels: ## Skip the GitHub Pull Request builds if any of the given GitHub labels match with the assigned labels in the PR.
+            - skip-ci
+        draft: true  ## Skip the GitHub Pull Request builds with Draft PRs.

.buildkite/hooks/pre-command

@@ -29,7 +29,8 @@ retry() {
   return 0
 }
 
-if [[ "$BUILDKITE_PIPELINE_SLUG" == "filebeat" || "$BUILDKITE_PIPELINE_SLUG" == "auditbeat" || "$BUILDKITE_PIPELINE_SLUG" == "heartbeat" || "$BUILDKITE_PIPELINE_SLUG" == "deploy-k8s" ]]; then
+
+if [[ "$BUILDKITE_PIPELINE_SLUG" == "beats" || "$BUILDKITE_PIPELINE_SLUG" == "filebeat" || "$BUILDKITE_PIPELINE_SLUG" == "auditbeat" || "$BUILDKITE_PIPELINE_SLUG" == "heartbeat" || "$BUILDKITE_PIPELINE_SLUG" == "deploy-k8s" ]]; then
   source .buildkite/env-scripts/env.sh
   source .buildkite/env-scripts/util.sh