Replace GH Action from tj-actions by custom code

The GitHub Actions build workflow includes external Actions from
3rd party repositories.
The functionality of tj-actions/verify-changed-files was used to
detect modifications of files under source control during the build
process.
The external action is removed and replaced by custom code.
This is less flexible, but does not require an external action in the
build toolchain.

Signed-off-by: Holger Friedrich <[email protected]>

Author: holgerfriedrich

.github/workflows/ci-build.yml

@@ -73,8 +73,10 @@ jobs:
           path: build.log
 
       - name: Verify Changed Files
-        uses: tj-actions/verify-changed-files@v20
         id: verify-changed-files
+        run: |
+          changed_files=$(git diff --name-only ${{ github.sha }} | tr '\n' ' ')
+          echo "changed_files=$changed_files" >> $GITHUB_OUTPUT
 
       - name: Fail on Changed Files
         if: steps.verify-changed-files.outputs.changed_files != ''