gitlab-ci: enable building the test image for VK unconditionally

It was diabled because RADV is the only driver that tests Vulkan
and running CTS on my personal machine and without recovery is
not safe enough for CI (too long and too unstable).

Now that we are going to test Fossilize with RADV, it's needed to
build the test image for VK unconditionally. As RADV now supports
creating NULL devices, the fossilize jobs can run everywhere.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3960>

.gitlab-ci.yml

@@ -138,18 +138,6 @@ x86_test-vk:
   extends: x86_build
   variables:
     DEBIAN_TAG: &x86_test-vk "2020-03-05"
-  # Can only be triggered manually on personal branches because RADV is the only
-  # driver that does Vulkan testing at the moment.
-  rules:
-    # Never build the test image for VK by default in the main project.
-    - if: '$CI_PROJECT_PATH == "mesa/mesa"'
-      when: never
-    # Never build the test image for VK by default for merge requests.
-    - if: '$CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'
-      when: never
-    # Otherwise, allow building it manually for personal branches.
-    - when: manual
-
 
 # Debian 9 based x86 build image (old LLVM)
 x86_build_old:
@@ -727,9 +715,8 @@ arm64_a306_gles2:
     # Never test RADV by default for merge requests.
     - if: '$CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'
       when: never
-    # Otherwise, allow testing RADV if the test image for VK has been manually
-    # started.
-    - when: on_success
+    # Otherwise, allow testing RADV manually for personal branches.
+    - when: manual
 
 radv_polaris10_vkcts:
   extends: