ci: inject gfx-ci/linux S3 artifacts without rebuilding containers

We need update kernel often. We need test kernel changes often.

Introduced `KERNEL_EXTERNAL_TAG` to differ between `KERNEL_TAG` which is
also used to rebuild the containers. We don't need rebuild containers
for the external kernel, so this way we don't have to.

Updating kernel goes wruuuuuum.

Signed-off-by: David Heidelberg <david.heidelberg@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23563>

src/broadcom/ci/gitlab-ci.yml

@@ -20,6 +20,8 @@
 .vc4-rules:
   stage: broadcom
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.never-post-merge-rules, rules]
     - !reference [.igalia-farm-rules, rules]
     - !reference [.gl-rules, rules]
@@ -43,6 +45,8 @@
 .v3d-rules:
   stage: broadcom
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.never-post-merge-rules, rules]
     - !reference [.igalia-farm-rules, rules]
     - !reference [.gl-rules, rules]
@@ -69,6 +73,8 @@
 .v3dv-rules:
   stage: broadcom
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.never-post-merge-rules, rules]
     - !reference [.igalia-farm-rules, rules]
     - !reference [.vulkan-rules, rules]

src/gallium/drivers/llvmpipe/ci/gitlab-ci-inc.yml

@@ -1,6 +1,8 @@
 .llvmpipe-rules:
   stage: software-renderer
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.gl-rules, rules]
     - changes: &llvmpipe_file_list
       - src/gallium/drivers/llvmpipe/**/*

src/gallium/drivers/softpipe/ci/gitlab-ci-inc.yml

@@ -1,6 +1,8 @@
 .softpipe-rules:
   stage: software-renderer
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.gl-rules, rules]
     - changes: &softpipe_file_list
       - src/gallium/drivers/softpipe/**/*

src/gallium/drivers/virgl/ci/gitlab-ci-inc.yml

@@ -1,6 +1,8 @@
 .virgl-rules:
   stage: layered-backends
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.gl-rules, rules]
     - !reference [.llvmpipe-rules, rules]
     - changes: &virgl_file_list

src/gallium/frontends/lavapipe/ci/gitlab-ci-inc.yml

@@ -1,6 +1,8 @@
 .lavapipe-rules:
   stage: software-renderer
   rules:
+    - if: $FORCE_KERNEL_TAG != null
+      when: never
     - !reference [.vulkan-rules, rules]
     - !reference [.gallium-core-rules, rules]
     - changes: &lavapipe_file_list