Add logic to download vendor scripts

.github/workflows/build-release.yml

@@ -13,6 +13,36 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@master
+      - name: Download vendor scripts
+        run: |
+          vendor_scripts=""
+          # Using `command | while read...` is more typical, but the inside of the `while`
+          # loop will run under a separate process this way, meaning that it cannot
+          # modify $vendor_scripts. See: https://stackoverflow.com/a/16855194
+          exec 3< <(
+            # Get minified versions of vendor scripts.
+            php bin/get-vendor-scripts.php
+            # Get non-minified versions of vendor scripts (for SCRIPT_DEBUG).
+            php bin/get-vendor-scripts.php debug
+          )
+          while IFS='|' read -u 3 url filename; do
+            echo "$url"
+            echo -n " > vendor/$filename ... "
+            http_status=$( curl \
+              --location \
+              --silent \
+              "$url" \
+              --output "vendor/_download.tmp.js" \
+              --write-out "%{http_code}"
+            )
+            if [ "$http_status" != 200 ]; then
+              error "HTTP $http_status"
+              exit 1
+            fi
+            mv -f "vendor/_download.tmp.js" "vendor/$filename"
+            vendor_scripts="$vendor_scripts vendor/$filename"
+          done
+          echo ::set-env name=vendor_scripts::$vendor_scripts
       - name: Install dependencies
         run: npm install
         env: