Add ccache to amd (#5555)

.buildkite/test-template-aws.j2

@@ -30,6 +30,7 @@ steps:
         command: bash .buildkite/run-amd-test.sh "cd {{ (step.working_dir or default_working_dir) | safe  }} ; {{ step.command  or (step.commands | join(" ; ")) | safe }}"
         env:
           DOCKER_BUILDKIT: "1"
+        priority: 100
         soft_fail: true
     {% endif %}
     {% endfor %}