CI: make test-artifacts repo/branch/job customizable

Allow choosing which artifacts branch and job to use for Linux. This
allows running the same tests for different Linux versions, without
duplicating a lot of yaml sections.

Similarly, make the repo path itself configurable too. The main purpose
is to ensure the test pipeline triggered from any repo will fetch linux
artifact from the right repo. But with a minor change of using that
variable for rootfs and microcode artifacts too, it allows testing
test-artifacts repo changes without needing to modify gitlab-ci.yml in
xen.git at all.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>

.gitlab-ci.yml

@@ -3,6 +3,18 @@ variables:
   SELECTED_JOBS_ONLY:
     description: "Regex to select only some jobs, must be enclosed with /. For example /job1|job2/"
     value: "/.*/"
+  ARTIFACTS_REPO:
+    description: "Path to the test-artifacts repo"
+    value: xen-project/hardware/test-artifacts
+  ARTIFACTS_BRANCH:
+    description: "Branch in test-artifacts to use"
+    value: master
+  LINUX_JOB_X86_64:
+    description: "Job name in test-artifacts to use for Linux x86_64"
+    value: linux-6.6.56-x86_64
+  LINUX_JOB_ARM64:
+    description: "Job name in test-artifacts to use for Linux arm64"
+    value: linux-6.6.86-arm64
 
 workflow:
   name: "$CI_PIPELINE_SCHEDULE_DESCRIPTION"