Will mirror updater give us neer sbcl?

hm...

PiperOrigin-RevId: 842968669

Author: Jonathan Godbout

.github/workflows/SBCL-test.yml

@@ -11,6 +11,14 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: clean apt
+        run: sudo apt clean
+
+      - name: Update mirror
+        run: |
+          APT_MIRROR=au
+          sudo sed --in-place --regexp-extended "s/(\/\/)(archive\.ubuntu)/\1${APT_MIRROR}.\2/" /etc/apt/sources.list
+
       - name: Update apt package list
         run: sudo apt update