Implement a cache for integration test (#649)

This PR divides the CI time by ~2

## Issue #

N/A

## Description of changes

This PR makes two changes to the integration tests workflow:

1. Replace the manual `git clone` checkout with `actions/checkout@v4` in
the `test-examples` job. The container image was updated from Amazon
Linux 2 to `swift:6.2` (Ubuntu-based), which supports Node.js-based
GitHub Actions. This also removes the now-unnecessary
`working-directory` overrides that pointed to the repository
subdirectory created by the manual clone.

2. Add SPM dependency caching (`actions/cache@v4`) to the
`test-examples`, `test-archive-plugin`, and `check-foundation` jobs.
Each example's `.build` directory is cached with a key scoped per
example name, avoiding cross-contamination between different dependency
sets.

## New/existing dependencies impact assessment, if applicable

No new dependencies were added to this change. This only adds the
`actions/cache@v4` GitHub Action to the CI workflow.

## Conventional Commits

`ci: switch to actions/checkout and add SPM dependency caching in
integration tests`

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

---------

Co-authored-by: Sebastien Stormacq <stormacq@amazon.lu>
Co-authored-by: Tim Condon <0xTim@users.noreply.github.com>

.github/workflows/integration_tests.yml

@@ -42,8 +42,8 @@ on:
       matrix_linux_swift_container_image:
         type: string
         # Note: we don't use Amazon Linux 2 here because zip is not installed by default.
-        description: "Container image for the matrix test jobs. Defaults to Swift 6.2 on Amazon Linux 2."
-        default: "swift:6.2-amazonlinux2"
+        description: "Container image for the matrix test jobs. Defaults to Swift 6.2"
+        default: "swift:6.2"
 
 ## We are cancelling previously triggered workflow runs
 concurrency:
@@ -66,35 +66,24 @@ jobs:
     container:
       image: ${{ matrix.swift.image }}
     steps:
-      # GitHub checkout action has a dep on NodeJS 20 which is not running on Amazonlinux2
-      # workaround is to manually checkout the repository
-      # https://github.com/actions/checkout/issues/1487
-      - name: Manually Clone repository and checkout PR
-        env:
-          PR_NUMBER: ${{ github.event.pull_request.number }}
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - name: Cache SPM dependencies
+        uses: actions/cache@v5
+        with:
+          path: Examples/${{ matrix.examples }}/.build
+          key: spm-${{ runner.os }}-${{ matrix.examples }}-${{ hashFiles(format('Examples/{0}/Package.swift', matrix.examples)) }}
+          restore-keys: |
+            spm-${{ runner.os }}-${{ matrix.examples }}-
+
+      - name: Install dependencies
         run: |
-          # Clone the repository
-          git clone https://github.com/${{ github.repository }}
-          cd ${{ github.event.repository.name }}
-
-          # Fetch the pull request
-          git fetch origin +refs/pull/$PR_NUMBER/merge:
-
-          # Checkout the pull request
-          git checkout -qf FETCH_HEAD
-
-      # - name: Checkout repository
-      #   uses: actions/checkout@v4
-      #   with:
-      #       persist-credentials: false
-
-      - name: Mark the workspace as safe
-        working-directory: ${{ github.event.repository.name }}  # until we can use action/checkout@v4
-        # https://github.com/actions/checkout/issues/766
-        run: git config --global --add safe.directory ${GITHUB_WORKSPACE}
+          apt-get -qq update && apt-get -qq -y install libssl-dev
 
       - name: Run matrix job
-        working-directory: ${{ github.event.repository.name }}  # until we can use action/checkout@v4
         env:
           COMMAND: ${{ inputs.matrix_linux_command }}
           EXAMPLE: ${{ matrix.examples }}
@@ -116,9 +105,15 @@ jobs:
         with:
           persist-credentials: false
 
-      - name: Mark the workspace as safe
-        # https://github.com/actions/checkout/issues/766
-        run: git config --global --add safe.directory ${GITHUB_WORKSPACE}
+      - name: Cache SPM dependencies
+        uses: actions/cache@v5
+        with:
+          path: |
+            Examples/${{ matrix.examples }}/.build/checkouts
+            Examples/${{ matrix.examples }}/.build/repositories
+          key: spm-${{ runner.os }}-${{ matrix.examples }}-${{ hashFiles(format('Examples/{0}/Package.swift', matrix.examples)) }}
+          restore-keys: |
+            spm-${{ runner.os }}-${{ matrix.examples }}-
 
       - name: Test the archive plugin
         env:
@@ -133,34 +128,19 @@ jobs:
     container:
       image: ${{ inputs.matrix_linux_swift_container_image }}
     steps:
-      # GitHub checkout action has a dep on NodeJS 20 which is not running on Amazonlinux2
-      # workaround is to manually checkout the repository
-      # https://github.com/actions/checkout/issues/1487
-      - name: Manually Clone repository and checkout PR
-        env:
-          PR_NUMBER: ${{ github.event.pull_request.number }}
-        run: |
-          # Clone the repository
-          git clone https://github.com/${{ github.repository }}
-          cd ${{ github.event.repository.name }}
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: false
 
-          # Fetch the pull request
-          git fetch origin +refs/pull/$PR_NUMBER/merge:
-
-          # Checkout the pull request
-          git checkout -qf FETCH_HEAD
-
-      # - name: Checkout repository
-      #   uses: actions/checkout@v4
-      #   with:
-      #     persist-credentials: false
-
-      - name: Mark the workspace as safe
-        working-directory: ${{ github.event.repository.name }}  # until we can use action/checkout@v4
-        # https://github.com/actions/checkout/issues/766
-        run: git config --global --add safe.directory ${GITHUB_WORKSPACE}
+      - name: Cache SPM dependencies
+        uses: actions/cache@v5
+        with:
+          path: Examples/APIGatewayV2/.build
+          key: spm-foundation-${{ runner.os }}-${{ hashFiles('Examples/APIGatewayV2/Package.swift') }}
+          restore-keys: |
+            spm-foundation-${{ runner.os }}-
 
       - name: Check for Foundation or ICU dependency
-        working-directory: ${{ github.event.repository.name }}  # until we can use action/checkout@v4
         run: |
           .github/workflows/scripts/check-link-foundation.sh