Adapt update script to avoid downloading again and reuse release files

script/update-truffleruby

@@ -2,19 +2,20 @@
 
 set -e
 
-if [ $# -ne 1 ]; then
-  echo "usage: $0 VERSION"
+if [ $# -ne 2 ]; then
+  echo "usage: $0 VERSION RELEASE_DIRECTORY"
   exit 1
 fi
 
 version="$1"
+release_directory="$2"
 file="share/ruby-build/truffleruby-${version}"
 
 add_platform() {
   platform="$1"
   basename="truffleruby-${version}-${platform}.tar.gz"
   url="https://github.com/oracle/truffleruby/releases/download/vm-${version}/${basename}"
-  sha256=$(curl -L "$url" | sha256sum | cut -d ' ' -f 1)
+  sha256=$(sha256sum "$release_directory/$basename" | cut -d ' ' -f 1)
 
   cat >> "$file" <<EOS
   install_package "truffleruby-${version}" "${url}#${sha256}" truffleruby