Restore bootstrap script for pre-Bake setup

Readme.md

@@ -15,12 +15,18 @@ This repository is now a single integrated Ruby project. The legacy Swift genera
 
 ## Requirements
 
-- Ruby `3.4.1` (see `.ruby-version`)
+- Ruby (see `.ruby-version`)
 - Bundler
 - `rbenv` recommended
 
 ## Setup
 
+```bash
+bin/bootstrap
+```
+
+Or manually:
+
 ```bash
 rbenv install -s "$(cat .ruby-version)"
 rbenv exec bundle install

bin/bootstrap

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+RUBY_VERSION="$(cat "$ROOT_DIR/.ruby-version")"
+
+if [[ "$(uname)" = "Linux" ]]; then
+  echo "*** installing Linux prerequisites"
+  sudo apt install -y \
+    build-essential \
+    git \
+    inotify-tools \
+    libffi-dev \
+    libyaml-dev \
+    pkg-config \
+    zlib1g-dev
+fi
+
+cd "$ROOT_DIR"
+
+if command -v rbenv >/dev/null 2>/dev/null; then
+  echo "*** using rbenv (ruby $RUBY_VERSION)"
+  rbenv install -s "$RUBY_VERSION"
+  rbenv exec bundle install
+else
+  echo "*** rbenv not found, using system Ruby"
+  bundle install
+fi
+
+echo "*** done"