gitlab-ci: Extract EDK2 job rules to reusable section

All jobs depending on 'docker-edk2' job must use at most all
the rules that triggers it. The simplest way to ensure that
is to always use the same rules. Extract all the rules to a
reusable section, and include this section (with the 'extends'
keyword) in both 'docker-edk2' and 'build-edk2' jobs.

The problem was introduced in commit 71920809ce ("gitlab-ci.yml:
Add jobs to build EDK2 firmware binaries"), but was revealed in
commit 1925468ddb ("docker: EDK2 build job depends on EDK2
container") and eventually failed on CI:
https://gitlab.com/qemu-project/qemu/-/pipelines/335995843

Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Message-Id: <20210714101003.3113726-1-philmd@redhat.com>

.gitlab-ci.d/edk2.yml

@@ -1,10 +1,22 @@
-docker-edk2:
- stage: containers
- rules: # Only run this job when the Dockerfile is modified
+# All jobs needing docker-edk2 must use the same rules it uses.
+.edk2_job_rules:
+ rules: # Only run this job when ...
  - changes:
+   # this file is modified
    - .gitlab-ci.d/edk2.yml
+   # or the Dockerfile is modified
    - .gitlab-ci.d/edk2/Dockerfile
+   # or roms/edk2/ is modified (submodule updated)
+   - roms/edk2/*
    when: always
+ - if: '$CI_COMMIT_REF_NAME =~ /^edk2/' # or the branch/tag starts with 'edk2'
+   when: always
+ - if: '$CI_COMMIT_MESSAGE =~ /edk2/i' # or last commit description contains 'EDK2'
+   when: always
+
+docker-edk2:
+ extends: .edk2_job_rules
+ stage: containers
  image: docker:19.03.1
  services:
  - docker:19.03.1-dind
@@ -24,16 +36,9 @@ docker-edk2:
  - docker push $IMAGE_TAG
 
 build-edk2:
+ extends: .edk2_job_rules
  stage: build
  needs: ['docker-edk2']
- rules: # Only run this job when ...
- - changes: # ... roms/edk2/ is modified (submodule updated)
-   - roms/edk2/*
-   when: always
- - if: '$CI_COMMIT_REF_NAME =~ /^edk2/' # or the branch/tag starts with 'edk2'
-   when: always
- - if: '$CI_COMMIT_MESSAGE =~ /edk2/i' # or last commit description contains 'EDK2'
-   when: always
  artifacts:
    paths: # 'artifacts.zip' will contains the following files:
    - pc-bios/edk2*bz2