Reorganize test-32bit prerequisites to explain libstdc++6:amd64

This uses the same array+comment style as in 8c71bd1 (#1672).

Author: EliahKagan

.github/workflows/ci.yml

@@ -203,9 +203,21 @@ jobs:
     steps:
       - name: Prerequisites
         run: |
-          dpkg --add-architecture amd64  # For 64-bit Node.js, for actions.
+          prerequisites=(
+            build-essential
+            ca-certificates
+            cmake
+            curl
+            git
+            jq
+            libssl-dev
+            libstdc++6:amd64  # To support external 64-bit Node.js for actions.
+            pkgconf
+          )
+          dpkg --add-architecture amd64
           apt-get update
-          apt-get install --no-install-recommends -y build-essential ca-certificates cmake curl git jq libssl-dev libstdc++6:amd64 pkgconf
+          apt-get install --no-install-recommends -y -- "${prerequisites[@]}"
+        shell: bash
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with: