[jjbb] enable multibranch job (#3)

Author: v1v

.ci/jobs/apm-agent-ruby.yml

@@ -0,0 +1,4 @@
+---
+- job:
+    name: apm-agent-ruby
+    project-type: folder

.ci/jobs/defaults.yml

@@ -0,0 +1,24 @@
+---
+
+##### GLOBAL METADATA
+
+- meta:
+    cluster: apm-ci
+
+##### JOB DEFAULTS
+
+- job:
+    view: APM-CI
+    project-type: multibranch
+    logrotate:
+      daysToKeep: 30
+      numToKeep: 300
+    number-to-keep: '100'
+    days-to-keep: '30'
+    concurrent: true
+    node: linux
+    periodic-folder-trigger: 1w
+    prune-dead-branches: true
+    publishers:
+    - email:
+        recipients: infra-root+build@elastic.co

.ci/jobs/ecs-logging-ruby-mbp.yml

@@ -0,0 +1,42 @@
+---
+- job:
+    name: apm-agent-ruby/ecs-logging-ruby-mbp
+    display-name: ECS logging Ruby
+    description: ECS logging Ruby
+    script-path: .ci/Jenkinsfile
+    scm:
+    - github:
+        branch-discovery: no-pr
+        discover-pr-forks-strategy: merge-current
+        discover-pr-forks-trust: permission
+        discover-pr-origin: merge-current
+        discover-tags: true
+        notification-context: 'apm-ci'
+        repo: ecs-logging-ruby
+        repo-owner: elastic
+        credentials-id: 2a9602aa-ab9f-4e52-baf3-b71ca88469c7-UserAndToken
+        ssh-checkout:
+          credentials: f6c7695a-671e-4f4f-a331-acdce44ff9ba
+        build-strategies:
+        - tags:
+            ignore-tags-older-than: -1
+            ignore-tags-newer-than: -1
+        - regular-branches: true
+        - change-request:
+            ignore-target-only-changes: false
+        clean:
+          after: true
+          before: true
+        prune: true
+        shallow-clone: true
+        depth: 3
+        do-not-fetch-tags: true
+        submodule:
+          disable: false
+          recursive: true
+          parent-credentials: true
+          timeout: 100
+          reference-repo: /var/lib/jenkins/.git-references/ecs-logging-ruby.git
+        timeout: '15'
+        use-author: true
+        wipe-workspace: 'True'