CI (Buildkite): llvmpasses: use the latest rootfs image (#41864)

(cherry picked from commit 01d439e)

Author: DilumAluthge

.buildkite/pipelines/main/misc/llvmpasses.yml

@@ -33,8 +33,8 @@ steps:
       - JuliaCI/julia#v1:
           version: 1.6
       - staticfloat/sandbox#v1:
-          rootfs_url: https://github.com/JuliaCI/rootfs-images/releases/download/v3.1/package_linux.x86_64.tar.gz
-          rootfs_treehash: "8c33c341a864852629b8aac01a6eb6a79b73570e"
+          rootfs_url: https://github.com/JuliaCI/rootfs-images/releases/download/v3.8/package_linux.x86_64.tar.gz
+          rootfs_treehash: "84a323ae8fcc724f8ea5aca5901bbbf4bda3e519"
           uid: 1000
           gid: 1000
           workspaces: