CI: use namespace.so (#31056)

* namespace

* mkdir

* fix

* restore only

* restore

* v3
old-commit-hash: 9ee0a8a2b1

.github/workflows/compile-openpilot/action.yaml

@@ -1,11 +1,5 @@
 name: 'compile openpilot'
 
-inputs:
-  cache_key_prefix:
-    description: 'Prefix for caching key'
-    required: false
-    default: 'scons'
-
 runs:
   using: "composite"
   steps:
@@ -24,4 +18,4 @@ runs:
       if: github.ref == 'refs/heads/master'
       with:
         path: .ci_cache/scons_cache
-        key: ${{ inputs.cache_key_prefix }}-${{ env.CACHE_COMMIT_DATE }}-${{ github.sha }}
+        key: scons-${{ runner.arch }}-${{ env.CACHE_COMMIT_DATE }}-${{ github.sha }}