workflows: src-mirror: use RunsOn 64cpu-linux-x64

Replace GitHub-hosted runner with RunsOn-hosted
runner.
This runner is 4x more powerful and 4x cheaper.

Signed-off-by: Mirko Covizzi <[email protected]>

Author: MirkoCovizzi

.github/workflows/src-mirror.yml

@@ -14,7 +14,9 @@ jobs:
 
   # Tar entire project west workspace, prune, and upload to artifact service.
   generate-src-mirror-package:
-    runs-on: ubuntu-24.04-16cores
+    runs-on:
+      - runs-on=${{ github.run_id }}
+      - runner=64cpu-linux-x64
     steps:
 
       - name: Set STABLE variable