[CI] Pass rate artifact (#968)

Upload pass rate report as job artifact instead of storing it in a
shared volume.

.github/workflows/build-test.yml

@@ -207,7 +207,12 @@ jobs:
       - name: Pass rate
         run: |
           python3 scripts/pass_rate.py --reports ~/reports
-          mkdir -p /cache/reports/pass-rate
-          TMPFILE=$(mktemp -p /cache/reports/pass-rate XXXXXXXXXX)
-          python3 scripts/pass_rate.py --reports ~/reports --json > $TMPFILE
-          mv $TMPFILE $TMPFILE.json
+          python3 scripts/pass_rate.py --reports ~/reports --json > pass_rate.json
+
+      - name: Upload pass rate report
+        # upload reports only for the default branch
+        if: github.ref_name == 'llvm-target'
+        uses: actions/upload-artifact@v4
+        with:
+          name: pass_rate-${{ join(matrix.*, '-') }}
+          path: pass_rate.json