Webhook cause duplicate jobs and enable shell-executor

Hi,

I am trying to use AWS CodeBuild as the runner for gitlab, I checked a few links:

• AWS CodeBuild: Self-managed GitLab runners in AWS CodeBuild
• AWS CodeBuild: Tutorial: Configure a CodeBuild-hosted GitLab runner
• AWS CodeBuild: AWS CodeBuild adds support for managed runners for GitLab Self-Managed
• AWS CodeBuild: Use runners with AWS CodeBuild
• ...

It basically works, but for an unknow reason:

• There are 2 jobs created, not just 1
• The job for the webhook is in stage external even though I never defined it
• The first of the 2 jobs is in fact using shell-executor which shouldn't be enabled (without the webhook, the pipeline is stuck and won't use the shell-executor)

workflow:
  name: HelloWorld

stages:
  - build

build-job:
  stage: build
  script:
    - echo "Hello World"
  tags:
    - codebuild-test-gitlab-runners-$CI_PROJECT_ID-$CI_PIPELINE_IID-$CI_JOB_NAME

Do you know why it happens ?