gitlab: drop $CI_PROJECT_DIR from cache path

The gitlab cache is limited to only handle content within the
$CI_PROJECT_DIR hierarchy, and as such relative paths are always
implicitly relative to $CI_PROJECT_DIR.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230801130403.164060-5-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.gitlab-ci.d/windows.yml

@@ -7,7 +7,7 @@
   cache:
     key: "${CI_JOB_NAME}-cache"
     paths:
-      - ${CI_PROJECT_DIR}/msys64/var/cache
+      - msys64/var/cache
   needs: []
   stage: build
   timeout: 80m