[CI] Actually fix detect-changes for large PRs (#17786)

Shown working
[here](https://github.com/sarnex/llvm/actions/runs/14203819229/job/39796735530?pr=2).

Signed-off-by: Sarnie, Nick <[email protected]>

Author: sarnex

.github/workflows/sycl-detect-changes.yml

@@ -19,16 +19,13 @@ jobs:
     steps:
       - name: Set changed_files
         id: changed_files
-        uses: actions/github-script@v7
-        with:
-          script: |
-            const changedFiles = context.payload.pull_request.changed_files;
-            console.log("Number of files changed:", changedFiles);
-            return { changed_file_cnt: changedFiles } ;
+        shell: bash
+        run: |
+          echo "changed_file_cnt=${{ github.event.pull_request.changed_files }}" >> $GITHUB_OUTPUT
 
       - name: Check file changes
         uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36
-        if: ${{ steps.changed_files.outputs.changed_file_cnt < 500 }}
+        if: steps.changed_files.outputs.changed_file_cnt < 500
         id: changes
         with:
           filters: |
@@ -91,7 +88,7 @@ jobs:
         uses: actions/github-script@v7
         with:
           script: |
-            if (context.payload.pull_request.changed_files < 500) {
+            if (${{steps.changed_files.outputs.changed_file_cnt}} < 500) {
               return '${{ steps.changes.outputs.changes }}';
             }
             // Treat everything as changed for huge PRs.