Use Fastlane to decrypt secrets in prototype build step

This is a followup to 6fce8c8

Unfortunately, we need to use the same configure implementation across
the whole CI automation due to existing compatibility bugs between the
Ruby and Rust versions

.buildkite/commands/build-prototype.sh

@@ -5,11 +5,8 @@ set -eu
 echo "--- :rubygems: Setting up Gems"
 install_gems
 
-echo "--- Installing Secrets"
-# This is a hack until our AMI has a newer version of glibc and openSSL
-./gradlew
-chmod +x vendor/configure/configure
-docker run -it --rm --workdir /app --env CONFIGURE_ENCRYPTION_KEY -v $(pwd):/app public.ecr.aws/automattic/android-build-image:4281c9e97b2d821df3de34c046b7c067499b35bb /bin/bash -c 'vendor/configure/configure apply'
+echo "--- :closed_lock_with_key: Installing Secrets"
+bundle exec fastlane run configure_apply
 
 echo "--- :hammer_and_wrench: Build and Test"
 bundle exec fastlane build_and_upload_prototype_build