github ci: Add platform prefix to testsuite-run results

Author: GHC GitLab CI

.github/workflows/ci.yml

@@ -68,7 +68,7 @@ jobs:
       uses: actions/upload-artifact@v4
       if: ${{ !cancelled() }} # upload test results even if the testsuite failed to pass
       with:
-        name: testsuite-results
+        name: ${{ matrix.plat }}-testsuite-results
         path: |
           _build/test-perf.csv
           _build/test-summary.txt