gitlab-ci: Replace YAML anchors by extends (cross_system_build_job)

'extends' is an alternative to using YAML anchors
and is a little more flexible and readable. See:
https://docs.gitlab.com/ee/ci/yaml/#extends

More importantly it allows exploding YAML jobs.

Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20201207131503.3858889-3-philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.gitlab-ci.d/crossbuilds.yml

@@ -1,5 +1,5 @@
 
-.cross_system_build_job_template: &cross_system_build_job_definition
+.cross_system_build_job:
   stage: build
   image: $CI_REGISTRY_IMAGE/qemu/$IMAGE:latest
   timeout: 80m
@@ -13,7 +13,7 @@
           xtensa-softmmu"
     - make -j$(expr $(nproc) + 1) all check-build
 
-.cross_user_build_job_template: &cross_user_build_job_definition
+.cross_user_build_job:
   stage: build
   image: $CI_REGISTRY_IMAGE/qemu/$IMAGE:latest
   script:
@@ -24,91 +24,91 @@
     - make -j$(expr $(nproc) + 1) all check-build
 
 cross-armel-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-armel-cross
 
 cross-armel-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-armel-cross
 
 cross-armhf-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-armhf-cross
 
 cross-armhf-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-armhf-cross
 
 cross-arm64-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-arm64-cross
 
 cross-arm64-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-arm64-cross
 
 cross-mips-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-mips-cross
 
 cross-mips-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-mips-cross
 
 cross-mipsel-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-mipsel-cross
 
 cross-mipsel-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-mipsel-cross
 
 cross-mips64el-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-mips64el-cross
 
 cross-mips64el-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-mips64el-cross
 
 cross-ppc64el-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-ppc64el-cross
 
 cross-ppc64el-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-ppc64el-cross
 
 cross-s390x-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: debian-s390x-cross
 
 cross-s390x-user:
-  <<: *cross_user_build_job_definition
+  extends: .cross_user_build_job
   variables:
     IMAGE: debian-s390x-cross
 
 cross-win32-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: fedora-win32-cross
 
 cross-win64-system:
-  <<: *cross_system_build_job_definition
+  extends: .cross_system_build_job
   variables:
     IMAGE: fedora-win64-cross