ci: Retry lint image building once after failure

The same was done for the other CI tasks in commit fa6aa9f42f. This may
guard against intermittent network issues to download the base image or
packages ...

.github/workflows/ci.yml

@@ -601,7 +601,7 @@ jobs:
       - name: CI script
         shell: python
         run: |
-          import os, shlex, subprocess, sys
+          import os, shlex, subprocess, sys, time
 
           def run(cmd, **kwargs):
               print("+ " + shlex.join(cmd), flush=True)
@@ -621,7 +621,10 @@ jobs:
               "."
           ]
 
-          run(build_cmd)
+          if run(build_cmd, check=False).returncode != 0:
+              print("Retry building image tag after failure")
+              time.sleep(3)
+              run(build_cmd)
 
           CIRRUS_PR_FLAG = []
           if '${{ github.event_name }}' == "pull_request":