Add ability to invoke action.sh outside of GitHub Action env

Author: socheatsok78

setup.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+SETUP_FLUTTER_WORKDIR=${SETUP_FLUTTER_WORKDIR:-"$(pwd)/.setup-flutter"}
+
+# Runner environment variables
+export RUNNER_TOOL_CACHE="$SETUP_FLUTTER_WORKDIR/tool_cache"
+export RUNNER_TEMP="$SETUP_FLUTTER_WORKDIR/temp"
+export RUNNER_ARCH=$(uname -m)
+export RUNNER_OS=$(uname -s | tr '[:upper:]' '[:lower:]')
+
+if [ "$RUNNER_OS" = "darwin" ]; then
+    export RUNNER_OS="macos"
+fi
+
+# GitHub Context
+export GITHUB_ENV="$SETUP_FLUTTER_WORKDIR/.env"
+export GITHUB_PATH="$SETUP_FLUTTER_WORKDIR/.path"
+
+# Create mock environment
+mkdir -p "$RUNNER_TOOL_CACHE" "$RUNNER_TEMP"
+
+# Run the action
+curl -fsSL "https://raw.githubusercontent.com/flutter-actions/setup-flutter/main/action.sh" | bash -s -- "$@"