Move macOS Bazel cache outside checkout

Scripts/ci/nscloud-cache.sh

@@ -132,8 +132,14 @@ if [[ -z "$cache_root" ]]; then
         break
       fi
     done
-  elif ensure_dir "$PWD/.nscloud-cache"; then
-    cache_root="$PWD/.nscloud-cache"
+  else
+    tmp_root="${RUNNER_TEMP:-${TMPDIR:-/tmp}}/burrow-nscloud-cache"
+    for candidate in "$tmp_root" "$PWD/.nscloud-cache"; do
+      if ensure_dir "$candidate"; then
+        cache_root="$candidate"
+        break
+      fi
+    done
   fi
 fi