resort to Swiftly to simplify locating swift dylib paths for samples

Author: ktoso

.github/scripts/prep-gh-action.sh

@@ -1,5 +1,8 @@
 #!/bin/bash
 
+# This script is reused from Swiftly itself, see:
+# https://github.com/swiftlang/swiftly/blob/main/scripts/prep-gh-action.sh
+#
 # This script does a bit of extra preparation of the docker containers used to run the GitHub workflows
 # that are specific to this project's needs when building/testing. Note that this script runs on
 # every supported Linux distribution and macOS so it must adapt to the distribution that it is running.

.github/workflows/pull_request.yml

@@ -142,6 +142,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Prepare CI Environment
         uses: ./.github/actions/prepare_env
+      - name: Prepare the action
+        run: ./scripts/prep-gh-action.sh --install-swiftly
       - name: "Verify sample: ${{ matrix.sample_app }}"
         run: .github/scripts/validate_sample.sh Samples/${{ matrix.sample_app }}