ci: fix stack cache for macOS

We now have two stack jobs for macOS, but they use the same cache, which
is very inefficient. Adding the architecture to the cache key will give
each of these jobs a separate cache.

.github/actions/cache-on-main/action.yaml

@@ -24,11 +24,11 @@ runs:
         path: ${{ inputs.path }}
         key: ${{ runner.os }}-${{ inputs.prefix }}-${{ inputs.suffix }}
         restore-keys: |
-          ${{ runner.os }}-${{ inputs.prefix }}-
+          ${{ runner.os }}-${{ runner.arch }}-${{ inputs.prefix }}-
     - uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
       if: ${{ !startsWith(github.ref, 'refs/heads/') && !(inputs.save-prs && startsWith(github.ref, 'refs/pull/'))  }}
       with:
         path: ${{ inputs.path }}
         key: ${{ runner.os }}-${{ inputs.prefix }}-${{ inputs.suffix }}
         restore-keys: |
-          ${{ runner.os }}-${{ inputs.prefix }}-
+          ${{ runner.os }}-${{ runner.arch }}-${{ inputs.prefix }}-