ci: Add .use-base-image template

And use it in jobs for images using another Mesa image as their base.

Should fix the build of images which don't use another Mesa image as
their base (by no longer setting the FDO_BASE_IMAGE variable).

Fixes: 0781d9825b "ci: Append $MESA_TEMPLATES_COMMIT to image tags"
Acked-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Andres Gomez <agomez@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7957>

.gitlab-ci.yml

@@ -226,7 +226,6 @@ success:
     # Otherwise, container jobs won't run
     - when: never
   variables:
-    FDO_BASE_IMAGE: "${CI_REGISTRY_IMAGE}/${MESA_BASE_IMAGE}:${MESA_BASE_TAG}-${MESA_TEMPLATES_COMMIT}"
     FDO_DISTRIBUTION_TAG: "${MESA_IMAGE_TAG}-${MESA_TEMPLATES_COMMIT}"
     FDO_DISTRIBUTION_VERSION: buster-slim
     FDO_REPO_SUFFIX: "debian/$CI_JOB_NAME"
@@ -234,6 +233,15 @@ success:
     # no need to pull the whole repo to build the container image
     GIT_STRATEGY: none
 
+.use-base-image:
+  extends:
+    - .container
+    # Don't want the .container rules
+    - .ci-run-policy
+  stage: container-2
+  variables:
+    FDO_BASE_IMAGE: "${CI_REGISTRY_IMAGE}/${MESA_BASE_IMAGE}:${MESA_BASE_TAG}-${MESA_TEMPLATES_COMMIT}"
+
 # Debian 10 based x86 build image base
 x86_build-base:
   extends:
@@ -244,9 +252,8 @@ x86_build-base:
 
 .use-x86_build-base:
   extends:
-    - x86_build-base
-    - .ci-run-policy
-  stage: container-2
+    - .fdo.container-build@debian
+    - .use-base-image
   variables:
     MESA_BASE_IMAGE: "debian/x86_build-base"
     MESA_BASE_TAG: *x86_build-base
@@ -331,9 +338,8 @@ x86_test-base:
 
 .use-x86_test-base:
   extends:
-    - x86_build-base
-    - .ci-run-policy
-  stage: container-2
+    - .fdo.container-build@debian
+    - .use-base-image
   variables:
     MESA_BASE_IMAGE: "debian/x86_test-base"
     MESA_BASE_TAG: *x86_test-base
@@ -377,9 +383,8 @@ arm_test-base:
 
 .use-arm_test-base:
   extends:
-    - arm_test-base
-    - .ci-run-policy
-  stage: container-2
+    - .fdo.container-build@debian
+    - .use-base-image
   variables:
     MESA_BASE_IMAGE: "debian/arm_test-base"
     MESA_BASE_TAG: *arm_test-base