GHA: download additional images when packaging

Pull in the Android stdlib when building Android installer MSI.

Author: hyp

.github/workflows/swift-toolchain.yml

@@ -3339,6 +3339,10 @@ jobs:
             cpu: x86_64
 
     steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: Android-stdlib-${{ matrix.arch }}
+          path: ${{ github.workspace }}/BuildRoot/Library/Developer/Platforms/Android.platform
       - uses: actions/download-artifact@v4
         with:
           name: Android-sdk-${{ matrix.arch }}