fix: ensure eicweb and ghcr oci buildcache are used for fetch too

mirrors.yaml.in

@@ -2,6 +2,10 @@ mirrors:
   eicweb:
     url: oci://${CI_REGISTRY}/${CI_PROJECT_PATH}/spack-${SPACK_VERSION}
     signed: false
+    fetch:
+      access_pair:
+      - ${CI_REGISTRY_USER}
+      - ${CI_REGISTRY_PASSWORD}
     push:
       access_pair:
       - ${CI_REGISTRY_USER}
@@ -9,6 +13,10 @@ mirrors:
   ghcr:
     url: oci://ghcr.io/eic/spack-${SPACK_VERSION}
     signed: false
+    fetch:
+      access_pair:
+      - ${GITHUB_REGISTRY_USER}
+      - ${GITHUB_REGISTRY_TOKEN}
     push:
       access_pair:
       - ${GITHUB_REGISTRY_USER}

spack-environment/packages.yaml

@@ -354,7 +354,7 @@ packages:
     - '@0.30.0'
   qt:
     require:
-    - '@5.15.11'
+    - '@5.15.12'
     - +opengl
   root:
     require: