ci: build-ami: Use arch in EXECUTION_ID (#2209)

Both run_id and postgres_version are same for both amd64 and arm64
matrix variants. I'm not exactly sure what the effects of sharing
EXECUTION_IDs could be but Release AMI Nix already does it so lets
assume its for a good reason. Something to untangle later.

Author: mmlb

.github/actions/build-ami/action.yml

@@ -49,7 +49,7 @@ runs:
       id: set-execution-id
       shell: bash
       run: |
-        EXECUTION_ID="${{ github.run_id }}-${{ inputs.postgres_version }}"
+        EXECUTION_ID="${{ github.run_id }}-${{ inputs.postgres_version }}-${{ inputs.arch }}"
         echo "EXECUTION_ID=$EXECUTION_ID" >> $GITHUB_ENV
         echo "execution_id=$EXECUTION_ID" >> $GITHUB_OUTPUT