[CI] add CI scripts separate from the workflows (#442)

_[One line description of your change]_

### Motivation:

_[Explain here the context, and why you're making that change. What is
the problem you're trying to solve.]_

### Modifications:

_[Describe the modifications you've done.]_

### Result:

_[After your change, what will change.]_

.github/workflows/scripts/check-archive-plugin.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the SwiftAWSLambdaRuntime open source project
+##
+## Copyright (c) 2017-2024 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+## Licensed under Apache License v2.0
+##
+## See LICENSE.txt for license information
+## See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+##
+## SPDX-License-Identifier: Apache-2.0
+##
+##===----------------------------------------------------------------------===##
+
+EXAMPLE=HelloWorld
+OUTPUT_DIR=.build/plugins/AWSLambdaPackager/outputs/AWSLambdaPackager
+OUTPUT_FILE=${OUTPUT_DIR}/MyLambda/bootstrap
+ZIP_FILE=${OUTPUT_DIR}/MyLambda/MyLambda.zip
+
+pushd Examples/${EXAMPLE} || exit 1
+
+# package the example (docker and swift toolchain are installed on the GH runner)
+LAMBDA_USE_LOCAL_DEPS=../.. swift package archive --allow-network-connections docker || exit 1
+
+# did the plugin generated a Linux binary?
+[ -f "${OUTPUT_FILE}" ]
+file "${OUTPUT_FILE}" | grep --silent ELF
+
+# did the plugin created a ZIP file?
+[ -f "${ZIP_FILE}" ]
+
+# does the ZIP file contain the bootstrap?
+unzip -l "${ZIP_FILE}" | grep --silent bootstrap
+
+echo "✅ The archive plugin is OK"
+popd || exit 1